GEOLOGICAL HANDBOOK

MINERAL A

BY: MAULANA ARSYAD

http://mineral.galleries.com/

THE MINERAL ACANTHITE /ARGENTITE

Chemistry: Ag2S, Silver Sulfide

Class: Sulfides

Uses: An ore of silver and as mineral specimens.

Specimens

Acanthite is the most important silver ore next to galena. Actually there is an argument to be made that acanthite could be the most important silver ore. Galena is a lead ore that often contains enough silver (usually about 1%) that when it is processed for its lead content the by-product silver supplies the majority of the world's needs. But most, if not all the silver in argentiferous galena is thought to actually be microscopic inclusions of acanthite crystals. Acanthite is often confused with the name argentite and it is no wonder. Several mineral guides interchange the names or combine the names as is done here. But the proper mineral name when referring to Ag2S at room temperatures is acanthite. Argentite is a name applied to one polymorph (meaning many shapes) of Ag2S. Acanthite and argentite have the same chemistry , Ag2S, but different structures. Argentite has an isometric structure and is only stable at temperatures above 173 degrees Celsius and if cooling from a melt, will form isometric crystals such as cubes, octahedrons and dodecahedrons. Upon cooling to below 173 degrees Celsius, argentite transforms from its isometric structure to the monoclinic structure of acanthite. The transformation often distorts the crystals to unrecognizable shapes, but some will still have an overall isometric crystal shape. These crystals are

called pseudomorphs (false shapes) as they are actually acanthite's crystals in the shape of argentite's crystals. Argentite has been historically used when referring to these crystals, but the acknowledgment of the true identity of the mineral requires the naming of these crystals (at lower temperatures) as acanthite. Acanthite, in addition to the crystals discussed above, forms interesting groupings of crystals. The crystals themselves are often distorted, but they group together into some intricate arborescent (branching) structures. Argentite comes from the Latin word for silver, argentum, from which the chemical symbol for silver, Ag, is also derived. Acanthite comes from the Greek word for thorn, acantha, in allusion to its typical crystal habits. Acanthite is generally easily identified although it may appear like galena and other silver sulfide minerals. The crystal habits discussed above are usually diagnostic enough, however the sectility test may be needed in some cases. Acanthite is sectile which means that it can be cut into by a knife just like lead.

Acanthite is generally a very valuable mineral specimen, due mostly to the high silver content and the rarity of good crystals. It is a pleasure to own fine acanthite specimens once they are finally procured. PHYSICAL CHARACTERISTICS:

Color is lead gray to black.

Luster is metallic.

Transparency: Crystals are opaque.

Crystal System: Monoclinic; 2/m below 173 degrees

Celsius (acanthite) and isometric; 4/m bar 3 2/m above (argentite).

Crystal Habits include rarely well formed pseudo:

cubes, octahedrons and dodecahedrons. Non-argentite crystals (those that formed below 173 degrees Celsius) of acanthite tend to be of a slender prismatic habit.

More commonly found massive and as coatings or as arborescent (branching) and reticulated groups.

Cleavage is absent.

Fracture is conchoidal.

Hardness is 2.5 - 3

Specific Gravity is approximately 5.5 - 5.8 (slightly

heavy even for metallic minerals).

Streak is a shiny black.

Other Characteristics: Sectile, meaning it can be cut with a knife like lead and fresh shiny surfaces will eventually form a dull coating after prolonged exposure to light (can be removed by ultrasonic treatment).

Associated Minerals include silver, quartz, bornite, gold, galena, proustite, pyrargyrite, stephanite and

other silver sulfide minerals.

Notable Occurrences include Guanajuato, Mexico;

Freiberg and Saxony, Germany; Cobalt, Ontario, Canada; Comstock Lode, Nevada and Butte, Montana, USA; Cornwall, England; Chile; Peru; Bolivia and especially Kongsberg, Norway.

Best Field Indicators are crystal habit, density,

softness, sectility, association with other silver sulfosalts and color.

THE MINERAL ACTINOLITE

Physical Properties: Click here

Chemistry: Ca2(Mg, Fe)5Si8O22(OH)2 , Calcium Magnesium Iron Silicate Hydroxide.

Class: Silicates

Subclass: Inosilicates

Group: Amphibole

Uses: asbestos and as ornamental stone used for carvings and semi-precious to precious stone used in jewelry

Specimens

Actinolite is a relatively common mineral in some metamorphic rocks. It belongs to a series with the minerals tremolite and ferro-actinolite. A series occurs when ions can freely

substitute between each other. In this case, when iron is predominant the mineral is ferro-actinolite and when magnesium is predominant the mineral is tremolite. Actinolite is the intermediate member. A variety of actinolite is composed of microscopically fibrous crystals (asbestos) and is called byssolite. Other minerals also form asbestos such as serpentine and the minerals of the series mentioned above. Serpentine asbestos is more widely used and of a better grade in general. Although asbestos has been shown to cause cancer in humans when inhaled in high enough concentrations, it still has many valuable applications. Asbestos is used for fire retardant materials and brake shoes and pads. Its prior use as insulation has been all but eliminated due to health concerns. A variety of actinolite, nephrite, is one of the two minerals called jade. The other jade mineral is jadeite. Jade has been used for eons in China and Central America as an ornamental and religious stone of deep significance. The nephrite jade was used mostly in China, although both have been used in both regions. Nephrite is more abundant than jadeite and has few color varieties, ranging only from creamy white to green. Simple actinolite occasionally forms interesting crystal habits and specimens. Crystals can be similar to hornblende, but are always translucent or even transparent. Typically they are

prismatic, flattened and elongated. Crystal specimens of actinolite can make very interesting mineral specimens. PHYSICAL CHARACTERISTICS:

Color is usually green.white or gray.

Luster is vitreous.

Transparency: examples are translucent to

transparent.

Crystal System is monoclinic; 2/m

Crystal Habits include the flattened prismatic and

elongated crystal with a dome-like termination that is actually a two of the four faces of a prism. Also as a fibrous mass (asbestos) and as a fibrous and very compact mass (nephrite jade).

Cleavage: is perfect in two directions at close to 60-

and 120-degree angles.

Fracture is splintery to uneven.

Hardness is 5.5 - 6.

Specific Gravity is approximately 2.9 - 3.3 (very

slightly above average for translucent minerals).

Streak is white.

Associated Minerals are quartz, lawsaonite, epidote and glaucophane.

Other Characteristics: the compact nephrite variety is

extremely tough and is actually stronger than steel.

Notable Occurrences include the Lake Baikal Region,

Russia; China; New Zealand; British Columbia, Canada and Taiwan.

Best Field Indicators are toughness (nephrite jade),

fibrosity (asbestos), typical green color, crystal habit and hardness.

THE MINERAL ADAMITE

Chemistry: Zn2AsO4(OH), Zinc Arsenate Hydroxide

Class: Phosphate Class

Subclass: Arsenates

Uses: Only as mineral specimens

Specimens

Adamite is a favorite among collectors of fluorescent minerals because of its consistent bright green fluorescence under short and long UV light. It also makes a wonderful mineral specimen in ordinary light. The typical lime green color of its adamantine (high luster) crystals set on top of its commonly associated red limonite matrix make specimens particularly attractive. Adamite is isostructural with the minerals cuproadamite - (Cu, Zn)2(AsO4)(OH), olivenite - Cu2AsO4(OH) and libethenite - Cu2PO4(OH). This means that they share the same symmetry and similar crystal shapes. Cuproadamite, which is intermediate between adamite and olivenite, is not completely recognized as a different mineral from adamite but is becoming accepted in ordinary usage. Adamite is not easy to mistake for any other mineral. Its bright green fluorescence, high luster, "sub" botyroidal crystal habit, high density, associations, typical bright green color and double triangle terminations make it both an exquisite specimen for a collection and an easy identification. Adamite typically shows a radiating habit that is intermediate between a simple druse and a botryoidal habit which gives a nice glimpse into how botryoidal habits form.

PHYSICAL CHARACTERISTICS:

Color is typically green due to trace amounts copper

and or uranium, yellow, rarely white and occasionally purple due to trace amount of cobalt.

Luster is adamantine.

Transparency: Crystals are transparent to translucent.

Crystal System is orthorhombic; 2/m 2/m 2/m

Crystal Habits include diamond shaped, wedge-like

prisms sometimes modified with minor prismatic faces and terminated by a double triangle. Mostly in druses and radiating clusters that can form wheel and wheat sheaf shapes. Rarely in a perfectly smooth botryoidal habit like smithsonite, but commonly found with well formed double triangular crystal terminations that sparkle on the top of the "sub" botryoidal surface.

Cleavage is perfect in two directions at non-right angles to each other (domal).

Fracture is conchoidal.

Hardness is 3.5.

Specific Gravity is approximately 4.4 (heavy for translucent minerals)

Streak is white to pale green.

Other Characteristics: Strongly fluoresces green in

short and long UV light.

Associated Minerals are legrandite, limonite, smithsonite, austinite, paradamite, aragonite, calcite, mimetite, conichalcite and other oxidation zone minerals.

Notable Occurrences include the famous mines at Mapimi, Mexico; also Greece and California and Utah, USA.

Best Field Indicators are crystal habit, color, luster,

density, fluorescences and associations.

THE MINERAL AEGIRINE

Chemistry: NaFeSi2O6 , Sodium Iron Silicate.

Class: Silicates

Subclass: Inosilicates

Group: Pyroxenes

Uses: Only as mineral specimens.

Specimens Aegirine, which is listed in some guides as acmite, forms impressive crystals that have become classics among collectors. These tall opaque monument-like crystals that jut majestically out from their host rocks are simply splendid. The steeply inclined pyramid on top of the prismatic crystals is very characteristic and thus diagnostic of aegirine. Its alternate name, acmite, comes from the Greek word for point. The name aegirine is after the Teutonic god of the sea, Aegir, and was given when the first specimens of the mineral were discovered in Norway. Aegirine is difficult to distinguish from its close cousin augite. Under normal circumstances, the steep pyramids of aegirine are the only point of differentiation (excuse the pun). PHYSICAL CHARACTERISTICS:

Color is black to greenish or brownish black.

Luster is vitreous.

Transparency: Specimens are generally opaque to

translucent.

Crystal System is monoclinic; 2/m

Crystal Habits include long prismatic crystals

terminated by a steep asymmetrical pyramid. Also as disseminated grains, compact and fibrous.

Cleavage is perfect in two directions at near 90 degree

angles.

Fracture is uneven.

Hardness is 6 - 6.5

Specific Gravity is approximately 3.5 - 3.6 (above

average for translucent minerals)

Streak is white or gray.

Other Characteristics: Splinters or thin edges are

translucent green.

Associated Minerals are augite, nepheline, andradite, barite, quartz, spessartine, riebeckite, biotite, sodalite and albite

Notable Occurrences include Mont Saint-Hilaire, Quebec, Canada; Kongsberg, Norway; Narsarssuk, Greenland; Kola Peninsula, Russia; Magnet Cove Arkansas, USA; Kenya; Scotland and Nigeria.

Best Field Indicators are crystal habit (especially its steep pyramids), density, cleavage, color and hardness.

THE MINERAL AESCHYNITE

Chemical Formula: (Y, Ca, Fe, Th)(Ti, Nb)2(O, OH)6, Yttrium Calcium Iron Thorium Titanium Niobium Oxide Hydroxide.

Class: Oxides and Hydroxides

Uses: A very minor ore of rare earth elements and as mineral specimens.

Specimens

Aeschynite is one of several Rare Earth Oxides and has two synonyms; "blomstrandine" and "priorite". Aeschynite's nomenclature is even more complex than this however. There are no less than three mineral names that begin with aeschynite and a few others that use aeschynite in their names. These minerals are all officially distinct minerals, but actually just differ in their respective compositions. The structure of these minerals is more or less unchanged. The prefixes or suffixes indicate which rare earth metal is predominant in the mineral as illustrated below:

Aeschynite-(Y) the yttrium rich aeschynite.

Aeschynite-(Ce) the cerium rich aeschynite.

Aeschynite-(Nd) the neodymium rich aeschynite.

Niobo-aeschynite-(Ce) the rich niobium/cerium

aeschynite.

Tantalaeschynite-(Y) the tantalum/yttrium rich

aeschynite.

Aeschynite referenced in guides and texts without any qualifiers usually refers to aeschynite-(Y) as it does here. Rare Earth Oxides such as aeschynite form from the leftover

elements that other minerals seem to not want. Other rare earth oxides such as fergusonite, samarskite and euxenite have

very similar properties to aeschynite and are often associated with each other, compounding the problem. Even the common oxide, rutile, is almost indistinguishable from these rare earth oxides without chemical tests when rutile is found massive. Aeschynite is found in rare earth rich granite pegmatites, a slow cooling igneous intrusive rock. Aeschynite is associated with minerals such as quartz, feldspars, zircon, columbite, xenotime, monazite, tantalite and other rare earth minerals.

Aeschynite forms well shaped crystals at times, is associated with other rare minerals and can be an interesting specimen in someone's collection. PHYSICAL CHARACTERISTICS:

Color is black to dark brown or yellowish brown in

smaller crystals.

Luster is vitreous to adamantine or pitchy when more massive.

Transparency: Crystals are nearly opaque in massive

forms and translucent in small crystals.

Crystal System is orthorhombic; 2/m 2/m 2/m

Crystal Habits include tabular to prismatic almost

blocky crystals, some with well formed domal terminations. Often embedded in the matrix of the host pegmatite; as well as granular and massive.

Cleavage is absent.

Fracture is conchoidal.

Hardness is 5 - 6

Specific Gravity is approximately 4.9 - 5.1 (heavy for

non-metallic minerals).

Streak is reddish brown or reddish yellow.

Other Characteristics: Weathered crystals/specimens are often coated with a limonite like earthy coating.

Associated Minerals include quartz, feldspars, euxenite, fergusonite, monazite, columbite, tantalite, allanite, gadolinite, xenotime and zircon.

Notable Occurrences include the Ural Mountains of

Russia; Urstad, Hittero, Norway and Madagascar.

Best Field Indicators are luster, fracture, color, streak,

associations, environment and specific gravity.

THE MINERAL ALBITE

Chemistry: NaAlSi3 O8, Sodium aluminum silicate.

Class: Silicates

Subclass: Tectosilicates

Group: Feldspars

Uses: ornamental stone, ceramics and mineral specimens.

Specimens

Albite is a common felspar and is the "pivot" mineral of two different feldspar series. It is most often associated with the plagioclase series where it is an end member of this series. The plagioclase series comprises felspars that range in chemical composition from pure NaAlSi3 O8 to pure CaAl2 Si2 O8 . The various plagioclase feldspars are identified from each other by gradations in index of refraction and density in the absence of chemical analysis and/or optical measurements. Albite is also an end member of the alkali or K-feldspars whose series

ranges from pure NaAlSi3 O8 to pure KAlSi3 O8. This series only exists at high temperatures with the mineral sanidine being the potassium, K, rich end member. At lower temperatures, the K-feldspars will seperate from the albite in a process called exsolution. The albite will form layers inside the k-feldspars crystals. Some times these layers are discernable to the naked eye and the stone is referred to as perthite. Albite by definition must contain no less than 90% sodium and no more than 10% of either potassium and/or calcium in the cation position in the crystal structure.. Albite is the last of the feldspars to crystallize from molten rock. The process of crystallization from a molten rock body serves to isolate rarer elements in the last stages of crystallization and therefore produces rare mineral species. Thus albite is often found with some lovely rare and beautiful minerals. Although usually not an exceptional collection mineral in itself, albite can be a nice accessory mineral to other mineral species. A variety associated with tourmaline is called cleavelandite and forms extremely thin, platy, white and sometimes very transparent crystals. All plagioclase feldspars show a type of twinning that is named after albite. Albite Law twinning produces stacks of twin layers that are typically only fractions of millimeters to several millimeters thick. These twinned layers can be seen as striation like grooves on the surface of the crystal and unlike true striations these also appear on the cleavage surfaces. The Carlsbad Law twin produces what appears to be two intergrown crystals growing in opposite directions. Two different twin laws, the Manebach and Baveno laws, produce crystals with one prominant mirror plane and penetrant angles or notches into the crystal. Although twinned crystals are common, single crystals showing a perfect twin are rare and are often collected by twin fanciers.

PHYSICAL CHARACTERISTICS:

Color is usually white (Albite is derived from the same

root word as albino) or colorless but can be shades of blue, yellow, orange and brown.

Luster is vitreous to dull if weathered..

Transparency crystals are translucent to opaque and

only sometimes transparent.

Crystal System is triclinic; bar 1

Crystal Habits include blocky, tabular and platy

crystals. The typical crystal has a nearly rectangular or square cross-section with slightly slanted dome and pinacoid terminations. A variety called Cleavelandite forms very thin platy crystals that can grow rather large (15+ cm across) but can maintain an even thickness of only a few millimeters. Twinning is almost universal in albite. Crystals can be twinned according to the Albite, Carlsbad, Manebach and Baveno laws. Albite is a common constituent of granitic and syenite rocks. Can also be massive.

Cleavage is perfect in one and good in another direction forming nearly right angled prisms.

Fracture is conchoidal.

Hardness is 6 - 6.5.

Specific Gravity is approximately 2.61 (average)

Streak is white.

Associated Minerals are quartz, tourmaline and muscovite.

Other Characteristics: index of refraction is 1.53.

Lamellar twinning may cause a grooved effect on cystal surfaces that appear as striations. Some albite may show an opalescence due to twinning and is referred to as moonstone.

Notable Occurrences include Labrador, Canada and the Scandinavian Peninsula.

Best Field Indicators are occurence, crystal habit,

twinning, striations, density and index of refraction.

ALEXANDRITE,

THE COLOR CHANGING VARIETY OF CHRYSOBERYL VARIETY INFORMATION:

VARIETY OF: Chrysoberyl , BeAl2 O4 .

USES: Gemstone.

BIRTHSTONE FOR: June

COLOR: varies from red to green.

INDEX OF REFRACTION: 1.745 - 1.757

BIREFRINGENCE: 0.009

HARDNESS: 8.5

CLEAVAGE: good in one direction, imperfect in another

CRYSTAL SYSTEM: orthorhombic

Pleochroic: strongly

For natural alexandrite mineral specimens see our For Sale or Sold lists

Alexandrite is named for the former czar of Russia, Alexander II, and was first discovered in the Ural Mountains of Russia, supposedly on the day of his birth. Chromium gives alexandrite its color and while, in most minerals, a trace element like chromium would provide only one color to the mineral, in alexandrite it gives it two! Coloring agents are dependent on the wavelength of light and the chemical bonds in the crystal to determine the color that they will cause. An element like copper, in normal light, can cause a green color in malachite and a blue color in azurite, it all depends on the character of the chemical bonding. In a single specimen of alexandrite, the chromium is in such a balanced situation that the color of the

specimen depends on the character of light that hits the crystal. If the light is natural sunlight or fluorescent light, the crystal will be green; however, if the light is incandescent light from a common indoor light bulb, then the crystal will appear red. Synthetic corundums spiked with trace elements that yield an alexandrite-like color change are sold as alexandrite on the gemstone market. These stones have a red-violet, near-amethyst color in incandescent light and a blue-violet color in daylight. They are far cheaper than natural alexandrites, which are some of the rarest and most expensive of gemstones.

THE MINERAL ALLANITE

Chemistry: (Ca, Ce, La, Y)2(Al, Fe)3(SiO4)3(OH), Calcium Cerium Lanthanum

Yttrium Aluminum Iron Silicate Hydroxide.

Class: Silicates

Subclass: Sorosilicates

Group: Epidote

Uses: As a source of rare earth metals and mineral specimens.

Specimens

Allanite, also known as "orthite" in Europe, is one of the most common rare earth minerals, which is somewhat of an oxymoron. Rare earth elements include many unusual and valuable metals. Up to 20% of allanite's weight could be composed of these rare earth elements, making allanite a

potentially valuable ore. Because of these rare earth metals, especially thorium, which are frequently radioactive, allanite is frequently slightly radioactive to no one's great surprise. The radioactivity, as in other radioactive minerals, can manifest itself in a couple of ways. Embedded crystals of allanite are frequently seen with a "halo" or dark ring; evidence of the radioactive effects on nearby minerals. Allanite can also become metamict. This is a condition found in radioactive minerals and results from the destructive effects of its own radiation on its crystal lattice. The effect can destroy a crystal lattice completely while leaving the outward appearance unchanged. The complete destruction of the allanite structure will produce a glassy hydrated substance. The hydration is facilitated by the metamictation. If just most of the elements that can be found in allanite were shown, then the formula would be written as (Ca, Ce, Y, La, Th, Na, K)2(Al, Fe, Be, Mn, Mg)3(SiO4)3(OH), or Calcium Cerium Yttrium lanthanum Thorium Sodium Potassium Aluminum Iron Beryllium Manganese Magnesium Silicate Hydroxide.

A mineral like allanite is sometimes referred to as a "trash can mineral" because it can possess elements that other minerals just seem to not want (i.e. the "trash") or is it because it can attract every stray element like a trash can attracts stray cats. whatever the case, the shorter formula version is used here and is more indicative of its general chemistry but does not reflect the broad chemical possibilities that allanite can produce. Allanite in the strictest sense is broken into three officially recognized minerals:

Allanite-(Ce) the cerium rich allanite, also the most

common and in general the one most often referred to as just allanite or orthite.

Allanite-(La) the lanthanum rich allanite.

Allanite-(Y) the yttrium rich allanite.

These minerals share the same structures and vary slightly in only a few of their properties. Chemical test would be required to differentiate them. Allanite, like other Epidote Group minerals, has some structural complexity in that it has both single silicate tetrahedrons, SiO4, and double silicate tetrahedrons, Si2O7. The formula of allanite could be expressed in a such a way so as to reflect this organization; (Ca, Ce, La, Y)2(Al, Fe)Al2O(SiO4)(Si2O7)(OH). The Al2O group represents the

parallel chains of AlO6 and AlO4(OH)2 octahedra that are the heart of the Epidote Group structure. The silicate groups and extra ions connect the chains together. Since the chains are parallel, the crystals tend to be prismatic. The chains are arranged in parallel planes and allanite's cleavage breaks the bonds between these planes. Allanite is found as an accessory mineral in several igneous rocks such as granites, syenites, diorites and their pegmatites and in a few metamorphic rocks as small embedded grains. It forms tabular crystals that can have excellent form and character. Remember, this is a slightly radioactive mineral and should be stored away from other minerals that are subject to damage from radioactivity and of course human exposure should be limited ! PHYSICAL CHARACTERISTICS:

Color is commonly black but can be brown to brownish violet if translucent.

Luster is vitreous to greasy.

Transparency: Crystals are commonly opaque but can

be found translucent.

Crystal System: Monoclinic; 2/m

Crystal Habits include long, somewhat prismatic or

tabular crystals with a typically dominant pinacoid that the crystal is often flattened against. The terminations are usually wedge shaped, more rarely tapered

pyramids. Also massive or as is most commonly the case, as embedded grains.

Cleavage poor in one direction, lengthwise.

Fracture is conchoidal.

Hardness is 5.5

Specific Gravity is 3.0 - 4.2

Streak is black.

Other Characteristics: Twinning may be seen as parallel grooves and allanite has slight radioactivity.

Associated Minerals include quartz, feldspars, biotite, thorite, xenotime, monazite and epidote

Notable Occurrences are widespread and include the

Ural Mountains of Russia; Falun, Ytterby and Sheppsholm, Sweden; Trimouns, France; Madagascar; the Eifel District of Germany; Spain; Otter Lake, Quebec and Madawaska, Ontario, Canada and Amelia Court House, Virginia; Barringer Hill, Texas; California; Franklin, New Jersey; Edenville and even New York, New York and New Mexico, USA.

Best Field Indicators are crystal habit, color, radioactivity, luster and hardness.

THE MINERAL ALMANDINE

Chemistry: Fe3Al2(SiO4)3, Iron Aluminum Silicate

Class: Silicates

Subclass: Nesosilicates

Group: Garnets

Uses: Gemstone and abrasive

See our natural Almandine Mineral Specimens For Garnet Jewelry, visit:

Almandine is the most common of the garnets and is usually the garnet found in garnet schists (a type of metamorphic rock composed mostly of mica). Precious transparent crystals are frequently used as gemstones along with its close cousin, Pyrope. Almandine, like other garnets, forms rounded crystals with 12 rhombic or 24 trapezoidal faces or combinations of these and some other forms. This crystal habit is classic for the garnet minerals. Almandine is the iron aluminum garnet. Magnesium can substitute for the iron and become more like pyrope, the magnesium aluminum garnet. Pure almandine and pure pyrope are rare in nature and most specimens are a percentage of the two. The change in density from almandine (4.3) to pyrope (3.6) is the only good test to determine a specimens likely identity. PHYSICAL CHARACTERISTICS:

Color is typically red to brown, sometimes with a tinge

of purple and sometimes a deep enough red to appear black.

Luster is vitreous.

Transparency crystals are transparent to translucent.

Crystal System is isometric; 4/m bar 3 2/m

Crystal Habits include the typical rhombic

dodecahedron. also seen is the 24 sided trapezohedron. Combinations of these forms are common and sometimes the rare faces of the hexoctahedron, a 48 sided crystal habit that rarely is seen by itself, can also combine with these other forms making very attractive, complex and multifaceted crystals. Massive occurrences are also common. Crystals typically embedded and isolated, from other alamadine crystals, in metamorphic rocks.

Cleavage is absent.

Fracture is conchoidal.

Hardness is 6.5 - 7.5

Specific Gravity is approximately 4.3 (above average

for translucent minerals and the highest density of all garnets)

Streak is white.

Associated Minerals are micas, staurolite, quartz and feldspars.

Other Characteristics: index of refraction is 1.83 and

multiplicity of faces give a striated appearance on some crystals.

Notable Occurrences include Wrangel Alaska;

Germany; Norway and India.

Best Field Indicators are crystal habit, color, density

and hardness.

THE MINERAL ALUMINUM

Chemistry: Al, Elemental Aluminum

Class: Elements

Subclass: Native Metals

Uses: Anywhere a light weight metal is needed, also explosives and medications.

Specimens

Native aluminum rarely occurs naturally in its elemental form, even though only oxygen and silicon are more abundant in the earth's crust. It has been found in volcanic muds and as tiny grains in highly unusual environments along with other elemental metals. Aluminum is known as aluminium outside of the United States. While aluminum is soft and weak in its pure form, when alloyed with other metals such as copper, magnesium or manganese its mechanical properties can improve greatly. Aluminum only has 60% of the electrical conductivity of copper, but its light weight and low cost make it a preferable metal for many electrical transmission applications. Aluminum is relatively strong (per unit of weight), as strong as steel although only about half as strong as titanium, which when combined with its low cost makes it a popular metal for building things from beer cans to lawn chairs to boats to airplanes. It is easy to manufacture since it is the second most malleable metal and the sixth most ductile - the only difficulty is in welding it. Actually, aluminum is extremely reactive, and any bare surface instantly grows a microscopic oxide layer (corundum) that is air tight and prevents further oxidation. In extreme heat, aluminum can begin to burn (similarly to magnesium), and can even burn under water by stealing the oxygen from water. The mixture called thermite is powdered aluminum and iron oxide. When ignited, the aluminum steals the oxygen from the rust, generating a great deal of heat and leaving molten iron. Also,

powdered aluminum is a primary ingredient in slow explosives such as fireworks. PHYSICAL CHARACTERISTICS:

Color is silvery-white.

Luster is metallic.

Transparency: Crystals are opaque.

Crystal System is isometric.

Crystal Habits are limited to microscopic inclusions

and as nodules in volcanic muds.

Cleavage is absent.

Hardness 1.5 (very soft)

Specific Gravity is 2.72 (very light for metals).

Streak is white.

Associated Minerals include gold, copper, and zinc.

Notable Occurrences are limited to Russia, Zaire, and

Baku, Azerbaidzhan.

Best Field Indicators: Rarity, color, softness, luster

and locality.

THE MINERAL ALUNITE

Chemistry: KAl3(SO4)2(OH)6, Potassium Aluminum Sulfate Hydroxide.

Class: Sulfates

Group: Alunite

Uses: As a minor source of alum, potassium and aluminum and as mineral specimens.

Specimens

Alunite is also known as alumstone and is a source of the chemical known as alum, KAl(SO4)2 - 12H2O. Some alunite has also been used to recover potassium and aluminum. Alunite forms from the action of sulfuric acids upon potassium rich feldspars in a process called "alunitization". The sulfuric acids accompany hydrothermal solutions, usually rich in certain ore metals. These solutions can result in large bodies of alunite, making alunite a rock forming mineral. As such, alunite can easily be mistaken for massive rock forming dolomite or limestone (calcite). An acid test should prove adequate in

identification as alunite does not bubble even when powdered. Alunite also forms at volcanic fumaroles. The symmetry of alunite is the same as the members of the Tourmaline Group. Crystals of alunite however do not form prismatic crystals like those of the typical tourmaline mineral. Alunite's crystals are more flattened and resemble nearly cubic rhombohedrons. The "rhombohedrons" are actually a combination of two trigonal pyramids. PHYSICAL CHARACTERISTICS:

Color is white or gray to reddish.

Luster is vitreous to pearly.

Transparency: Crystals are transparent to translucent.

Crystal System is trigonal; 3 m

Crystal Habits include tabular to flattened

rhombohedral looking crystals. The "rhombohedrons" are actually a combination of two trigonal pyramids. Crystals are somewhat scarce, small and usually line

the fissures in alunite rocks, more commonly as earthy masses, films or crusts, botryoidal and granular.

Cleavage is fair in one direction (basal), but only seen

in the larger crystals.

Fracture is conchoidal to uneven.

Hardness is 3.5 - 4.

Specific Gravity is approximately 2.7 - 2.8+ (average

for translucent minerals)

Streak is white.

Other Characteristics: Some specimens fluoresce a nice orange color under longwave UV light. Does not react to acids except to slowly dissolve, unlike dolomite and calcite. Also pyroelectric and piezoelectric.

Notable Occurrences include Marysvale, Utah; Red

Mountain, Custer County, Colorado and Goldfield district, Nevada, USA and Tolfa, Italy.

THE MINERALOID AMBER

Chemistry: Approximately C10H16O; Succinic acid.

Class: Mineraloids

Uses: Ornamental stone, gemstone and semi-precious stone.

The Physical Properties of Amber.

Specimens

Amber, or fossil tree sap, was made famous in the movie "Jurassic Park". Amber is a beautiful stone that is cut and

polished and used as a valuable gemstone. It is also a fossil and can contain many preserved insects and other animals and plants that are tens of millions of years old. The odd inclusions that are often seen in amber usually add to amber's unique look and in many cases greatly increase its value. The fossils that are encased in amber probably got there when they flew or crawled on to the fresh seeping sap and then got stuck. The sap oozed over the trapped animals and perhaps fell to the ground and was later covered by dirt and debris. The sap later hardened and became a fossil. The fossils are mostly insects such as gnats, flies, wasps, bees and ants. Occasionally more exotic insects are trapped in the amber such as grasshoppers, preying mantises, beetles, moths, termites, butterflies, etc. Other non-insect animals are found in amber too such as spiders, centipedes, scorpions and even frogs and lizards. No really large animals like mammals or birds are seen in amber but feathers and fur have been seen. Invaluable plant remains have also been found in amber including flowers, mushroom caps, seeds, leaves, stems, pine needles and pine cones. The rarity of the trapped fossils controls the value of the amber more so than the quality of the amber. Remember these are fossils and are not the same species that are alive today. Amber has greatly increased the knowledge of the evolution of insects and plants as well as enlivening the interest in paleontology in general. Amber is often imitated by plastics, colored glasses and some modern tree resins. However, its hardness is usually greater and it is tougher than other resins. Its low specific gravity (amber can float on salt water) and inclusions can distinguish it from plastics and glasses. PHYSICAL CHARACTERISTICS:

Color is amber yellow to orange.

Luster is resinous.

Transparency: Transparent to translucent.

Crystal System does not apply because amber is amorphous (meaning it does not have an ordered

structure).

Habits include nodules embedded in shales or

sandstones and those that are washed up on beaches.

Fracture is conchoidal.

Hardness is 2+.

Specific Gravity is approximately 1.1 (extremely light

and can float in salty water).

Streak is white.

Other Characteristics: Can be burned, fluorescent

under UV light and is much tougher (will not crumble as easily) than modern tree resins.

Notable Occurrences include all Baltic countries;

Venezuela; Russia; Romania; Burma; in coal seams in Wyoming, USA and the Dominican Republic.

Best Field Indicators are color, density, toughness,

softness and trapped insects.

THE MINERAL AMBLYGONITE

Chemistry: (Li, Na)AlPO4(F, OH), Lithium Sodium Aluminum Phosphate Fluoride Hydroxide.

Class: Phosphates

Group: Amblygonite

Uses: As a source of lithium and phosphorus, as gemstones and as mineral specimens.

Specimens

Amblygonite is a relatively common phosphate mineral. It is found in lithium and phosphate rich pegmatites as a primary mineral. At times it makes up a significant percentage of the rock although this fact may be overlooked. Amblygonite, as it turns out, is easily confused for other host rock members such as quartz and albite. The general appearance of amblygonite does resemble these two minerals especially the albite but it can be differentiated with a flame test for lithium, density and by its unusual cleavage. Amblygonite's name comes from the Greek words for "blunt angles" in allusion to its variously angled cleavages. Amblygonite has no less than four different directions of cleavage at different angles from one another and with different qualities of cleavage. This is very different from quartz which has no cleavage and albite which has only two directions of cleavage at nearly 90 degrees. Amblygonite has a fairly compact structure. This fact gives rise to a somewhat high specific gravity. Of course a specific gravity of around 3.05 is not considered very high in the mineral kingdom. But a look at amblygonite's formula shows the elements sodium, lithium, aluminum, hydrogen, fluorine, oxygen and phosphorous. None of these elements are heavy and a mineral composed of these elements would be expected

to have a specific gravity lower than 3. Both quartz and albite have lower specific gravities than amblygonite. Since amblygonite has lithium in its formula, it gives a reliable lithium result with a flame test. Powdered amblygonite which is placed in a gas flame will produce a brightly colored red flame. This is evidence for the presence of lithium. In amblygonite's chemistry, the lithium and sodium substitute for each other but there is a greater percentage of lithium than sodium. A mineral with the same structure and chemistry as amblygonite but with more sodium than lithium is called natramblygonite. There is also substitution between the

hydroxide and fluorine. Amblygonite also forms a solid solution series with the often associated mineral montebrasite and

differs from amblygonite by being richer in hydroxide instead of fluorine. The structures of the two minerals are the same and there are no discernible differences in physical properties between the two. In fact many specimens labeled amblygonite are in fact montebrasite. Gem quality amblygonite is mined in Brazil and the regions formerly known as Burma. These gems are an attractive yellow color and have an index of refraction of 1.61 and 1.64. This is a relatively low index of refraction but is higher than beryl or quartz and on par with topaz and tourmaline.

Amblygonite, montebrasite, natramblygonite, natromontebrasite, and a mineral named tavorite all belong to a group of minerals called the Amblygonite Group. The members of the Amblygonite Group are triclinic and have the general formula of ABPO4(F, OH). The A ion can be lithium and/or sodium and the B ion can be either aluminum or iron. Tavorite's formula for example is LiFePO4OH. PHYSICAL CHARACTERISTICS OF AMBLYGONITE:

Color is generally white or creamy, but can also be

colorless or pale yellow, green, blue, beige, gray or pink.

Luster is vitreous to greasy and pearly on cleavage

surfaces.

Transparency: Specimens are translucent to less commonly transparent.

Crystal System is triclinic, bar 1.

Crystal Habits include short prismatic, tabular or

equant crystals referred to as lath-shaped, but more commonly found as anhedral masses and compact grains. Twinning forms elongated, flatten crystals. Lamellar twinning is sometimes seen.

Cleavage is in four directions all with varying quality

with one direction being perfect, two directions being good and one direction being only distinct. All cleavage angles are non-right angles.

Fracture is uneven to conchoidal.

Hardness is 5.5 - 6

Specific Gravity is approximately 2.98 - 3.11 (slightly

above average).

Streak is white.

Other Characteristics: When powdered and placed in

a gas flame, it gives the flame a bright red color and this indicates the presence of lithium. Some specimens are fluorescent orange in long-wave UV light.

Associated Minerals include lepidolite, quartz, albite, elbaite, topaz, cassiterite, apatite, brazilianite, beryllonite, montebrasite, triphylite, lithiophilite and spodumene

Notable Occurrences are Minas Gerais, Brazil;

Montebras, France; Germany; Varutrask, Sweden; Sakangyi, Burma; Yellowknife, Northwest Territories, Canada. In the United States localities include Pala District of San Diego County, California; Newry, Hebron, Buckfield and Topsham, Maine; Taos County, New Mexico; Yavapai County, Arizona and the Black Hills area of South Dakota.

Best Field Indicators are density, associations,

environment, lithium flame test and especially the numerous cleavage angles.

AMETHYST, THE PURPLE VARIETY OF QUARTZ

VARIETY INFORMATION:

Variety of: Quartz , SiO2 .

Uses: Gemstones and ornamental stones.

Birthstone for: February

Color: various shades of purple.

Index of refraction: 1.544-1.553

Birefringence: 0.009

Hardness: 7

Cleavage: none

Crystal system: trigonal

Pleochroic: no

For natural amethyst mineral specimens see our For Sale or Sold lists

Amethyst is the purple variety of quartz and is a popular gemstone. If it were not for its widespread availability, amethyst would be very expensive. The name "amethyst" comes from the Greek and means "not drunken." This was maybe due to a belief that amethyst would ward off the effects of alcohol, but most likely the Greeks were referring to the almost wine-like color of some stones that they may have encountered. Its color is unparalleled, and even other, more expensive purple

gemstones are often compared to its color and beauty. Although it must always be purple to be amethyst, it can and does have a wide range of purple shades. Amethyst can occur as long prismatic crystals that have a six sided pyramid at either end or can form as druzes that are crystalline crusts that only show the pointed terminations. As a mineral specimen, amethyst is popular for its color and nice crystal shapes that produce a handsome, purple, sparkling cluster. However, amethyst is not the same everywhere. Different localities can produce a unique amethyst to that particular region or even to that particular mine. Experts can often identify the source mine that a particular amethyst came from. The key to this is the specimen's color, shape of crystal, inclusions, associations and character of formation. The following is a list of many of the more noteworthy localities and some of the attributes that characterize the amethyst found there.

Vera Cruz, Mexico -- very pale, clear, prismatic

crystals that are sometimes double terminated and have grown on a light colored host rock. Crystals are typically phantomed, having a clear quartz interior and an amethyst exterior. Some are sceptered and phantomed.

Guerrero, Mexico -- dark, deep purple, prismatic crystals that radiate outward from a common attachment point. Often the crystals are phantomed opposite of Vera Cruz amethyst having a purple interior with a clear or white quartz exterior. These are some of the most valuable amethysts in the world.

Minas Gerais and Rio Grande do Sul, Bahaia, Brazil

-- crystals form in druzy crusts that line the inside of sometimes large volcanic rock pockets or "vugs". Some of the vugs form from trees that were engulfed in a lava flow millions of years ago and have since withered away. Other vugs are just gas bubbles in the lava.

Some vugs can be quite large. The crystals that form are usually light to medium in color and only colored at the tops of the crystals. Most clusters form with gray, white and blue agate and have a green exterior on the vugs. Calcite sometimes is associated and inclusions of cacoxenite are common.

Maraba, Brazil -- large crystals with unattractive

surfaces that are of a pale to medium color and often carved or cut into slices.

Thunder Bay, Canada -- a distinct red hematite

inclusion just below the surface of the crystals is unique to this locality. Clusters are druzy crusts that line the fissures formed in ancient metamorphic rocks.

Uruguay -- crystals are dark to medium and form in

druzy crusts that line the inside of volcanic vugs that have a gray or brown exterior. The crystals are usually colored throughout, unlike the Brazilian crystals, and form with a multicolored agate that often contains reds, yellows and oranges. Often amethyst- coated stalactites and other unusual formations occur inside these vugs.

Africa -- crystals are usually large but not attractive.

However, the interior color and clarity are excellent and polished slices and carvings as well as many gemstones are prized and admired.

Maine, USA -- Dark druzy clusters that are not widely

distributed today.

North Carolina, USA -- Druzy clusters that have a

bluish-violet tint.

Pennsylvania, USA -- druzy clusters that filled

fractures in metamorphic rocks. They are generally a brownish purple and patchy in color.

Colorado, USA -- druzy clusters form crusts inside of

fissures in sandstone, often on top of a crust of green fluorite. Crystals are dark but rather small.

Italy -- both Vera Cruz like crystals, although not as

well defined, and large parallel growth clusters with good evenly distributed color.

Germany -- associated with colorful agates that form a

druzy light-colored crust.

Ural Mountains, Russia -- a very clear and dark

variety that is cut for fine expensive gemstones, natural uncut clusters are rarely on the market.

Often cut gems of amethyst are graded using the terms: Siberian, Uruguayan or Bahain; to represent high medium and low grade respectively, regardless of the actual source. Because of the patchyness of the color distribution in the crystals, Amethyst is often cut as brilliant round cuts to maximize the color. Other cuts can be used when the color is better distributed. The color purple is traditionally the color of royalty and amethyst has been used since the dawn of history to adorn the rich and powerful monarchs and rulers. Today, amethyst is a lovely and affordable gemstone that is fortunately available in a wide variety of cut and uncut stones that we can all possess and admire. Amethyst is only one of several quartz varieties. Other varieties that form macroscopic (large enough to see) crystals are as follows:

Citrine is a yellow to orange gemstone variety that is rare in nature but is often created by heating Amethyst.

Milky Quartz is the cloudy white variety.

Rock crystal is the clear variety that is also used as a gemstone.

Rose quartz is a pink to reddish pink variety.

Smoky quartz is the brown to gray variety.

THE MINERAL ANALCIME

Chemistry: NaAlSi2O6-H2O, Hydrated Sodium Aluminum Silicate

Class: Silicates

Subclass: Tectosilicates

Group: Zeolites

Uses: mineral specimen and chemical filter.

Specimens

Analcime is a popular and interesting mineral. It is sometimes known as analcite, although analcime is preferred. It is one of the few minerals that characteristically forms its own unique crystal. Well, not quite its own unique crystal, but pretty close. It forms the isometric trapezohedron. The minerals of the garnet group and high temperature leucite are the only common

minerals that will also form the trapezohedron. The trapezohedron has 24 deltoid-shaped faces, where each face occupies one third of the position of a single octahedron's face. Distinguishing analcime from the garnets and leucite is relatively easy in some cases. The garnets are much harder and usually deeply colored. Leucite has a much lower density and usually has a dull luster. Also leucite is typically embedded in host rock where as analcime, when displaying good crystals and not massive or granular, is loose or attacted to other minerals in volcanic cavities. Analcime, AlSi2O6-H2O is actually distantly related to leucite, KAlSi2O6. Leucite is a member of the feldspathoid group of minerals. Minerals whose chemistries are close to that of the alkali feldspars but are poor in silica (SiO2) content, are called feldspathoids. Feldspathoids are commonly found in silica-poor igneous rocks, where analcime is sometimes present as well.

Analcime is sometimes placed in the feldspathoid group since its chemistry and occassional occurrences are similar. Analcime's structure however has a typical zeolite openness about it that allows large ions and molecules to reside and actually move around inside the overall framework. The structure contains large open channels that allow water and large ions to travel into and out of the crystal structure. The size of these channels controls the size of the molecules or ions, and therefore a zeolite like analcime can act as a chemical sieve. PHYSICAL CHARACTERISTICS:

Color is clear, white or gray, with greenish, yellowish

and reddish tints possible.

Luster is vitreous.

Transparency: crystals are transparent to translucent.

Crystal System is isometric; 4/m bar 3 2/m

Crystal Habits include the characteristic

trapezohedron as well as the rare cube modified by trapezohedral faces. Also granular and massive.

Cleavage is absent.

Fracture is uneven.

Hardness is 5 - 5.5.

Specific Gravity is approximately 3.2 (average)

Streak is white.

Associated Minerals are quartz, calcite, serandite, apophyllite, natrolite, stilbite, heulandite and other zeolites.

Notable Occurrences include Mont St. Hilaire,

Quebec; Iceland; several localities in Oregon, Colorado and New Jersey, USA; Nova Scotia and Switzerland.

Best Field Indicators are crystal habit, density, low

hardness, luster and associations.

THE MINERAL ANAPAITE

Chemistry: Ca2Fe(PO4)2 - 4H2O, Hydrated Calcium Iron Phosphate

Class: Phosphates

Uses: only as a mineral specimen.

Specimens

Anapaite is rare and beautiful phosphate mineral. Or is it? Some mineral purists would dispute anapaite's inclusion into the mineral kingdom. The reason is that anapaite has a somewhat organic origin. In true pure mineralogical tradition, a mineral must have inorganic origins (ie. it is not made by a plant or animal). Anapaite is found in some fossil shell remains. But does this mean that the shell or bivalve formed the anapaite or did it just provide the needed calcium or change the environment of crystallization (such as the pH) needed for anapaite to form? If anapaite is excluded, it will be the mineral kingdom's loss! For anapaite is a truly beautiful mineral. Its lime green color is attractive and is a jewel inside the otherwise uncrystallized remains of an ancient fossil shell. The scene almost reminds you of a virtual green pearl. The triclinic crystals of anapaite are indistinct and this is very diagnostic, believe it or not! Perhaps it is the way or the environment in which anapaite forms, but the crystals look more like glass shards than like true crystals. Despite the lack of distinct forms, anapaite crystals are very different and would be a nice addition to anyone's collection.

PHYSICAL CHARACTERISTICS:

Color is commonly green or white.

Luster is vitreous.

Transparency crystals are transparent to translucent.

Crystal System is triclinic, bar 1

Crystal Habits include characteristically indistinct

prismatic crystals and aggregates.

Hardness is 3.5

Specific Gravity is approximately 2.8 (average for

translucent minerals)

Streak is white.

Associated Minerals are limonite and vivianite.

Anapaite often forms in fossil clam shells, coal beds (rarely) or phosphatic geodes.

Notable Occurrences include Anapa (hence the name), Taman Peninsula, Russia; Kerch Peninsula, Crimea, Ukraine; Bellaver de Cerdena, Spain; Kings County, California, USA and Germany.

Best Field Indicators are crystal habit, localities,

associations with fossils and phosphatic geodes and color.

THE MINERAL ANATASE

Chemical Formula: TiO2, Titanium Oxide

Class: Oxides and Hydroxides

Uses: A very minor ore of titanium and as mineral specimens.

Specimens

Anatase is a polymorph with two other minerals. The minerals rutile and brookite as well as anatase all have the same chemistry, TiO2, but they have different structures. At higher temperatures, about 915 degrees Celsius, anatase will automatically revert to the rutile structure. Rutile is the more common and the more well known mineral of the three, while anatase is the rarest. Anatase shares many of the same or nearly the same properties as rutile such as luster, hardness and density. However due to structural differences anatase and rutile differ slightly in crystal habit and more distinctly in cleavage. Anatase and rutile have the same symmetry, tetragonal 4/m 2/m 2/m, despite having different structures. In Rutile, the structure is based on octahedrons of titanium oxide which share two edges of the octahedron with other octahedrons and form chains. It is the chains themselves which are arranged into a four-fold symmetry. In anatase, the octahedrons share four edges hence the four fold axis. Crystals of anatase are very distinctive and are not easily confused with any other mineral. They form the eight faced tetragonal dipyramids that come to sharp elongated points. The elongation is pronounced enough to distinguish this crystal form from octahedral crystals, but there is a similarity. In fact anatase is wrongly called "octahedrite" in spite of the difference in forms. Of course "tetragonal dipyramidite" does not sound right either! Nice specimens of anatase are associated with quartz and are considered classics in the mineral world. The good luster, well formed crystal shape and interesting character make anatase a popular mineral for collectors. PHYSICAL CHARACTERISTICS:

Color is brown to black, also yellow and blue.

Luster is adamantine to submetallic.

Transparency crystals are opaque.

Crystal System is tetragonal; 4/m 2/m 2/m

Crystal Habits include the typical tetragonal

dipyramids that come to sharp elongated terminations points. These crystals look like stretched out octahedrons.

Cleavage is perfect in the basal direction and in four directions, pyramidal.

Fracture is subconchoidal.

Hardness is 5.5 - 6

Specific Gravity is 3.8 - 3.9 (average for metallic

minerals)

Streak is white.

Other Characteristics: Crystals are easily altered in

nature and sometimes pitted.

Associated Minerals include brookite, rutile, quartz, feldspars, apatite, hematite, chlorite, micas, calcite and sphene.

Notable Occurrences include Somerville,

Massachusetts and Gunnison Co., Colorado, USA; Tavistock, Devon, England; Austria; Diamantina District, Brazil; in the French Alps and at the Binnatal area of Switzerland.

Best Field Indicators are crystal habit, luster,

cleavage, density, streak, associations and locality.

THE MINERAL ANDALUSITE

Chemistry: Al2 SiO5, Aluminum Silicate

Class: Silicates

Subclass: Nesosilicates

Uses: in the manufacture of spark plugs etc, as a gemstone and as mineral specimens.

Specimens

Andalusite is a polymorph with two other minerals; kyanite and sillimanite. A polymorph is a mineral that shares the same chemistry but a different crystal structure with another, or other, minerals. A unique variety of andalusite is called "chiastolite". It contains black or brown clay and/or carbonaceous material inclusioned in the crystal. These inclusions are arranged in regular symmetrical shapes. Usually they are in the form of a cross or X. PHYSICAL CHARACTERISTICS:

Color is white, red, brown, orange and green.

Luster is vitreous.

Transparency crystals are transparent to translucent.

Crystal System is Orthorhombic; 2/m2/m2/m

Crystal Habits include prismatic crystals with a square

cross section terminated by a pinacoid. also massive and granular.

Cleavage is good in two directions.

Fracture is splintery to subconchoidal.

Hardness is 7.5

Specific Gravity is approximately 3.15+ (above

average)

Streak is white.

Associated Minerals are cordierite, biotite, feldspars,

quartz, kyanite and sillimanite.

Other Characteristics: dark inclusions produce

cruciform shapes in the variety, chiastolite. Index of refraction is 1.632-1.638.

Notable Occurrences include Andalusia, Spain;

Austria; California, USA and China.

Best Field Indicators are crystal habit, color,

inclusions (if present) and hardness.

THE MINERAL ANDERSONITE

Chemistry: Na2CaUO2(CO3)3-6H2O, Hydrated Sodium Calcium Uranyl Carbonate

Class: Carbonates

Uses: very minor ore of uranium and as mineral specimens.

Specimens

Andersonite is a rare uranyl carbonate mineral, that was only described in the last half century. It has a luster that seems to glow and in fact it is very fluorescent. Andersonite specimens

will usually glow a bright lemon yellow in ultraviolet light. The mineral is formed as a secondary mineral and as an efflorescent crust in uranium mines. Efflorescent means it forms

on the surface of a rock by the evaporation of water when in contact with the dry air of the mine. Thus, some andersonite specimens are the result of human intervention (albeit unintentional) and some minerologists do not consider these to be pure mineral specimens. Andersonite's lovely color and unique glow, as well as it's rarity and fluorescence, make it a wonderful mineral for rare mineral collectors. Remember, this is a radioactive mineral and should be stored away from other minerals that are affected by radioactivity and human exposure should definitely be limited. PHYSICAL CHARACTERISTICS:

Color is yellow to a yellowish green.

Luster is vitreous to pearly.

Transparency crystals are commonly translucent.

Crystal System is trigonal.

Crystal Habits include small rhombohedral crystals

that have angles close to 90 degrees, making them pseudocubic. Also found commonly as crusts.

Cleavage is perfect in three directions forming rhombs.

Fracture is conchoidal.

Hardness is 2.5

Specific Gravity is 2.9 (average).

Streak is pale yellow.

Associated Minerals are gypsum and other uranium

carbonates such as bayleyite, Mg2(UO2)(CO3)3-18H2O and liebigite, Ca2(UO2)(CO3)4-11H2O.

Other Characteristics: radioactive, and fluoresces

bright lemon-yellow under ultraviolet light.

Notable Occurrences include the Hillside Mine,

Bagdad, Arizona and the Jim Thorpe Mine, Pennsylvania, USA.

Best Field Indicators are its crystal habit, radioactivity,

fluorescence and associations.

THE MINERAL ANDESINE

Chemistry: Na(70-50%) Ca(30-50%) (Al, Si)AlSi2 O8, Sodium calcium aluminum silicate.

Class: Silicates

Subclass: Tectosilicates

Group: Feldspars

Uses: only as mineral specimens.

Specimens

Andesine is only a minor constituent in most granites and syenites. But is the dominant feldspar in certain igneous rocks called, appropriately andesites. It is also found in some metamorphic rocks as a minor constituent. Andesine is a member of the Plagioclase Feldspar Group. The plagioclase series comprises minerals that range in chemical composition from pure NaAlSi3 O8, Albite to pure CaAl2 Si2 O8 , anorthite. Andesine by definition must contain 70-50% sodium to 30-50% calcium in the sodium/calcium position of the crystal structure. The various plagioclase feldspars are identified from each other by gradations in index of refraction and density in the absence of chemical analysis and/or optical measurements. All plagioclase feldspars show a type of twinning that is named after albite. Albite Law twinning produces stacks of twin layers that are typically only fractions of millimeters to several millimeters thick. These twinned layers can be seen as striation like grooves on the surface of the crystal and unlike true striations these also appear on the cleavage surfaces. The Carlsbad Law twin produces what appears to be two intergrown crystals growing in opposite directions. Two different twin laws,

the Manebach and Baveno laws, produce crystals with one prominant mirror plane and penetrant angles or notches into the crystal. Although twinned crystals are common, single crystals showing a perfect twin are rare and are often collected by twin fanciers. PHYSICAL CHARACTERISTICS:

Color is mostly white or gray

Luster is vitreous to dull if weathered..

Transparency crystals are translucent to transparent.

Crystal System is triclinic; bar 1

Crystal Habits include blocky, or tabular crystals.

Crystals have a nearly rectangular or square cross-section with slightly slanted dome and pinacoid terminations. Twinning is almost universal in all plagioclases. Crystals can be twinned according to the Albite, Carlsbad, Manebach and Baveno laws.

Cleavage is perfect in one and good in another direction forming nearly right angled prisms.

Fracture is conchoidal.

Hardness is 6 - 6.5.

Specific Gravity is approximately 2.68-2.71 (average)

Streak is white.

Associated Minerals are biotite, hornblende, quartz and k-feldspars.

Other Characteristics: index of refraction is 1.545-

1.562. Lamellar twinning may cause a grooved effect on cystal and cleavage surfaces that appear as striations.

Notable Occurrences include Greenland; Andes

Mountains (hence the name Andesine) and Norway.

Best Field Indicators are occurence, twinning

striations, density and index of refraction.

THE MINERAL ANDRADITE

Chemistry: Ca3Fe2(SiO4)3, Calcium iron silicate

Class: Silicates

Subclass: Nesosilicates

Group: Garnets

Uses: Gemstone and abrasive

See our natural Andradite Mineral Specimens For Garnet Jewelry, visit:

Andradite, like other garnets, forms rounded crystals with 12 rhombic or 24 trapezoidal faces or combinations of these and some other forms. This crystal habit is classic for the garnet minerals. Andradite is the calcium iron garnet and forms in contact or regional metamorphic enviroments as does grossular, the calcium aluminum garnet. It is believed that these garnets form from the metamorphism of impure siliceous limestones. Andradite has many varieties based on color.

Melanite is the black variety.

Demantoid is the bright green variety and is

sometimes cut as a gem.

Topazolite is the yellow variety and is also

occassionally cut as a gem. PHYSICAL CHARACTERISTICS:

Color is typically greenish gray to green but also black,

yellow and rarely colorless.

Luster is vitreous.

Transparency crystals are transparent to translucent.

Crystal System is isometric; 4/m bar 3 2/m

Crystal Habits include the typical rhombic

dodecahedron. also seen is the 24 sided trapezohedron. Combinations of these forms are common and sometimes the rare faces of the hexoctahedron, a 48 sided crystal habit that rarely is seen by itself, can also combine with these other forms making very attractive, complex and multifaceted crystals. Massive occurrences are also common. Commonly forms crust that shows many rhombic faces

Cleavage is absent.

Fracture is conchoidal.

Hardness is 6.5 - 7.5

Specific Gravity is approximately 3.8+ (above average

for translucent minerals).

Streak is white.

Associated Minerals are micas, chlorite, diopside and serpentine.

Other Characteristics: index of refraction is 1.89

(highest of the garnets)

Notable Occurrences include Arizona; ural mountains in Russia; Italy and California..

Best Field Indicators are crystal habit, color, index of

refraction and hardness.

THE MINERAL ANHYDRITE or ANGELITE

Chemistry: CaSO4, Calcium Sulfate

Class: Sulfates

Uses: in the manufacture of some cement, a source of sulfate for sulfuric acid.

Specimens Anhydrite is a relatively common sedimentary mineral that forms massive rock layers. Anhydrite does not form directly, but is the result of the dewatering of the rock forming mineral Gypsum (CaSO4-2H2O). This loss of water produces a reduction in volume of the rock layer and can cause the formation of caverns as the rock shrinks. Good mineral specimens of Anhydrite were extremely rare dispite its common occurrance. However, fine specimens of Anhydrite have been found in Mexico and Peru that show good crystal habit, a nice blue color and even a play of light internally in the crystal. Lilac blue Anhydrate is sometimes called Angelite, for it's "Angelic" color. PHYSICAL CHARACTERISTICS:

Color is ordinarily white, gray or colorless but also blue

to violet.

Luster is vitreous.

Transparency crystals are transparent to translucent.

Crystal System is orthorhombic; 2/m 2/m 2/m

Crystal Habits include the tabular, rectangular box

formed by three pinacoids, often elongated in one direction forming a prismatic crystal. Most commonly massive and granular.

Cleavage is in three directions forming rectangles, but

perfect in one, very good in another and only marginally good in the third direction.

Fracture is conchoidal.

Hardness is 3.5

Specific Gravity is approximately 3.0 (average for

translucent minerals)

Streak is white.

Associated Minerals are calcite, halite, and ocassionally sulfides such as galena and pyrite.

Other Characteristics: some specimens fluoresce under UV light.

Notable Occurances include Mexico; Peru; Germany

and New Mexico.

Best Field Indicators are crystal habit, rectangular

and non-uniform cleavage and low density.

THE MINERAL ANORTHITE

Chemistry: CaAl2 Si2 O8, Calcium aluminum silicate.

Class: Silicates

Subclass: Tectosilicates

Group: Feldspars

Uses: only as mineral specimens.

Specimens

Anorthite is an end member and one of the rarer members of the plagioclase series. The plagioclase series comprises minerals that range in chemical composition from pure NaAlSi3 O8, Albite to pure CaAl2 Si2 O8 , anorthite. Anorthite by definition must contain no more than 10% sodium and no less than 90% calcium in the sodium/calcium position in the crystal structure. The various plagioclase feldspars are identified from each other by gradations in index of refraction and density in the absence of chemical analysis and/or optical measurements.

All plagioclase feldspars show a type of twinning that is named after albite. Albite Law twinning produces stacks of twin layers that are typically only fractions of millimeters to several millimeters thick. These twinned layers can be seen as striation like grooves on the surface of the crystal and unlike true striations these also appear on the cleavage surfaces. The Carlsbad Law twin produces what appears to be two intergrown crystals growing in opposite directions. Two different twin laws, the Manebach and Baveno laws, produce crystals with one prominant mirror plane and penetrant angles or notches into the crystal. Although twinned crystals are common, single crystals showing a perfect twin are rare and are often collected by twin fanciers. PHYSICAL CHARACTERISTICS:

Color is usually white, gray or colorless but can be pale

shades of other colors.

Luster is vitreous to dull if weathered..

Transparency crystals are translucent to opaque and

only sometimes transparent.

Crystal System is triclinic; bar 1

Crystal Habits include blocky, or tabular crystals.

Rarely are free crystals seen but they have a nearly rectangular or square cross-section with slanted dome and pinacoid terminations. Twinning is almost universal in all plagioclases. Crystals can be twinned according to the Albite, Carlsbad, Manebach and Baveno laws. Anorthite is usually found in contact metamorphic limestones and as a constituent in mafic igneous rocks.

Cleavage is perfect in one and good in another

direction forming nearly right angled prisms.

Fracture is conchoidal.

Hardness is 6 - 6.5.

Specific Gravity is approximately 2.76 (average)

Streak is white.

Associated Minerals are biotite, augite, hornblende and pyroxenes.

Other Characteristics: index of refraction is 1.575 to 1.591. Lamellar twinning may cause a grooved effect on cystal and cleavage surfaces that appear as striations.

Notable Occurrences include Lake Co, California;

Franklin, New Jersey and Italy.

Best Field Indicators are occurence, twinning

striations, density and index of refraction.

THE MINERAL ANTHOPHYLLITE

Chemistry: (Mg, Fe)7Si8O22(OH)2 , Magnesium Iron Silicate Hydroxide.

Class: Silicates

Subclass: Inosilicates

Group: Amphibole

Uses: Are limited to some asbestos uses and as mineral specimens.

Specimens

Anthophyllite is a common component of some metamorphic and metasomatic rocks. Its name comes from the Latin word for clove and is an allusion to its typical and distinct clove-brown color. Although it can be differentiated from other amphiboles by its white to brown color, it is often indistinguishable from other amphiboles such as cummingtonite. Cummingtonite and

anthophyllite are actually polymorphs, a situation where two minerals share the same chemistry but have different structures (poly=many, morphs=shapes). Diamond and graphite are the

most famous examples of polymorphism. In the case of anthophyllite and cummingtonite; anthophyllite is orthorhombic and cummingtonite is monoclinic. Anthophyllite is metamorphic and is found in gneisses and schists derived from magnesium rich igneous or dolomitic sedimentary rocks. It also forms from the retrograde metamorphism of other metamorphic minerals and from the metasomatic alteration of olivine and other ultramafic minerals

when these minerals are subjected to pressure in the presence of water. Under different conditions (such as more water), serpentine would be the mineral produced from the alteration of olivine. Like serpentine, some forms of anthophyllite are asbestos-form and can be used as asbestos. Asbestos has many industrial uses despite some health risks and is made of different minerals all with a fibrous habit. Serpentine and tremolite

asbestos are considered the better varieties due to their greater flexibility and tensile strength, but anthophyllite asbestos has its uses such as in refractory cements. Although individual well formed crystals of anthophyllite are very rare, some aggregate specimens of anthophyllite are striking and can make nice collection pieces. One variety found at Butte, Montana even displays a nice blue schiller effect. PHYSICAL CHARACTERISTICS:

Color is usually various shades of brown such as yellow-brown, green-brown or brownish-gray, but also green, off-white or gray.

Luster is vitreous to dull or silky in fibrous forms.

Transparency: Crystals are translucent to opaque.

Crystal System is orthorhombic; 2/m 2/m 2/m.

Crystal Habits include prismatic often aggregated

crystals and fibrous, asbestos-like masses.

Cleavage: is good in two directions at 56 and 124

degree angles forming wedge shapes fragments.

Fracture is easy and splintery.

Hardness is 5.5 - 6.

Specific Gravity is approximately 2.9 - 3.4 (average to

slightly above average).

Streak is gray.

Other Characteristics: Weakly pleochroic and a blue schiller effect is seen in some specimens from Butte, Montana.

Associated Minerals are talc, cordierite and phlogopite.

Notable Occurrences include Butte, Montana;

Delaware County, Pennsylvania; California; Arizona and Franklin County, North Carolina, USA; Ontario, Canada; Greenland; Kongsburg, Norway and Italy.

Best Field Indicators are crystal habit, fracture,

cleavage, color, streak and hardness.

THE MINERAL NATIVE ANTIMONY

Chemistry: Sb, Elemental Antimony

Class: Elements

Group: Arsenic

Uses: A very minor ore of antimony and as mineral specimens.

Specimens

Antimony does not often form in its elemental state and is far more common in sulfides and sulfosalts such as stibnite, tetrahedrite, bournonite, boulangerite and jamesonite. It is also found in some oxides such as valentinite, stibiconite and senarmontite Due to the abundance of these antimony

bearing ores and the rarity of native antimony, it is never an important ore of itself. Native antimony is nearly indistinguishable from native arsenic. However the garlic odor which is sometimes found on

arsenic specimens is not a characteristic of antimony and antimony does not tarnish as quickly or as severely as arsenic. PHYSICAL CHARACTERISTICS:

Color is tin-white to a steel gray which can tarnish to

darker grays.

Luster is metallic but the tarnish will often dull the

luster.

Transparency: Crystals are opaque.

Crystal System is trigonal; bar 3 2/m

Crystal Habits include pseudocubic rhombohedral

crystals. More commonly found massive, botryoidal, lamellar and radiating.

Cleavage is perfect in one direction (basal).

Fracture is uneven.

Hardness is 3 - 3.5

Specific Gravity is 6.6 - 6.7+ (heavy for a metallic mineral)

Streak is tin-white to gray.

Associated Minerals include sphalerite, stibnite and nickeline.

Other Characteristics: Does not have a garlic odor.

Notable Natural Occurrences include Chihuahua,

Mexico; Wolfe Co., Quebec, Canada and Kern Co., California, USA.

Best Field Indicators are density, softness, color,

crystal habits, lack of smell and associations.

THE MINERAL ANTLERITE

Chemistry: Cu3SO4(OH)4, Copper Sulfate Hydroxide.

Class: Sulfates

Uses: A minor ore of copper and as mineral specimens.

Specimens

Antlerite has been an important ore of copper and forms nice mineral specimens. It typically forms tabular to acicular or fibrous crystals. The acicular crystals often form aggregates of randomly organized coatings and tufts. Its green color is usually a deep and attractive shade. It is formed from the oxidation of copper ore minerals along with other oxidation zone minerals. Once thought to be a rare mineral, antlerite was discovered to be the chief ore at the Chuquicamata copper mines in Chile. Since then its presence has been confirmed at several other copper mines around the world. Antlerite is similar to other green copper minerals that form in oxidation zones such as the carbonate mineral malachite, the halide mineral atacamite and the closely related sulfate mineral brochantite. This brings up a number of identification problems. Acicular malachite will effervesce in warm hydrochloric acid and antlerite will not. Atacamite is slightly softer and is usually less transparent. Brochantite is all but indistinguishable by ordinary means although its terminations are typically more rounded than the terminations of antlerite.

PHYSICAL CHARACTERISTICS:

Color is a bright emerald green or dark green to almost

black.

Luster is vitreous.

Transparency: Crystals are transparent to translucent.

Crystal System is orthorhombic; 2/m 2/m 2/m

Crystal Habits include small tabular crystals and

acicular or fibrous crystal aggregates that form into coatings and tufts. Also found in veins and as reniform, massive or granular specimens.

Cleavage is perfect in one direction and poor in another.

Fracture is uneven.

Hardness is 3.5

Specific Gravity is approximately 3.9 (above average for translucent minerals)

Streak is pale green.

Other Characteristics: Does not effervesce in

hydrochloric acid and crystals can be vertically striated.

Associated Minerals are limonite, brochantite, cuprite, malachite, gypsum, chalcanthite, atacamite and azurite.

Notable Occurrences include Chuquicamata, Chile;

Mexico and the Antler mine (from where it gets its name) and Bisbee, Arizona, Nevada, California, New Mexico and Utah, USA.

Best Field Indicators are crystal habit, associations,

hardness, cleavage, non-reaction to hydrochloric acid and color.

THE MINERAL APATITE

Chemistry: Ca5(PO4)3(OH,F,Cl), Calcium (Fluoro, Chloro, Hydroxyl) Phosphate

Class: Phosphates

Group: Apatite

Uses: as a source of phosphorous to be used in fertilizer, rarely as a gemstone and as a mineral specimen.

Specimens

Apatite is actually three different minerals depending on the predominance of either fluorine, chlorine or the hydroxyl group. These ions can freely substitute in the crystal lattice and all three are usually present in every specimen although some specimens have been close to 100% in one or the other. The rather non-inventive names of these minerals are Fluorapatite, Chlorapatite and Hydroxylapatite. The three are usually considered together due to the difficulty in distinguishing them in hand samples using ordinary methods. An irony of the name apatite is that apatite is the mineral that makes up the teeth in all vertebrate animals as well as their bones. Get it? Apatite - teeth! Anyway, the name apatite comes from a Greek word meaning to decieve in allusion to its similarity to other more valuable minerals such as olivine, peridot and beryl.

Apatite is widely distributed in all rock types; igneous, sedimentary and metamorphic, but is usually just small disseminated grains or cryptocrystalline fragments. Large well formed crystals though can be found in certain contact metamorphic rocks. Very gemmy crystals of apatite can be cut

as gems but the softness of apatite prevents wide distribution or acceptance of apatite as a gemstone. PHYSICAL CHARACTERISTICS:

Color is typically green but also yellow, blue, reddish

brown and purple.

Luster is vitreous to greasy and gumdrop.

Transparency: Crystals are transparent to translucent.

Crystal System is hexagonal; 6/m

Crystal Habits include the typical hexagonal prism with

the hexagonal pyramid or a pinacoid or both as a termination. Also accicular, granular, reniform and massive. A cryptocrystalline variety is called collophane and can make up a rock type called phosphorite and also can replace fossil fragments.

Cleavage is indistinct in one basal direction.

Fracture is conchoidal.

Hardness is 5.

Specific Gravity is approximately 3.1 - 3.2 (average

for translucent minerals)

Streak is white.

Associated Minerals are hornblende, micas, nepheline and calcite.

Other Characteristics: An unusual "partially

dissolved" look similar to the look of previously sucked on hard candy.

Notable Occurrences include Durango, Mexico; Bancroft, Ontario; Germany and Russia.

Best Field Indicators are crystal habit, color, hardness

and look.

THE MINERAL APOPHYLLITE

Chemistry: (K,Na)Ca4Si8O20(F,OH) - 8H2O, Hydrated Potassium Calcium Sodium Silicate Fluoride Hydroxide.

Class: Silicates

Subclass: Phyllosilicates

Group: Apophyllite

Uses: Only as mineral specimens.

Physical Properties

Specimens

Apophyllite, whose name roughly means "to leaf apart" in Greek, is a mineral classic. It was given its name because crystals tend to peel or flake apart when they are heated due to the loss of water molecules. Although not that well-known by the general public, apophyllite is quite popular among mineral collectors. It is probably the first exotic mineral that a young collector will own after filling up on specimens of calcite, quartz, pyrite, galena, mica, fluorite, gypsum, apatite, etc,

etc. After these common minerals, apophyllite seems like a real rarity and it offers so much to the collector. It has beauty, pastel colors, a bright luster, interesting well formed habits, unusual associations with other exotic minerals and recently large amounts of quality specimens have become available at amazingly low prices from just a decade ago. What more could a collector want in a mineral? Unfortunately, apophyllite is not a mineral ! Not officially at least. Apophyllite is a general term for three official minerals that are similar in their chemistry and physical properties. Apophyllite is not the only mineral err . . . non-mineral that this

has happened to; see these non-minerals: apatite, olivine, serpentine and chlorite. Below is a comparison of the three official apophyllite minerals.

THE OFFICIAL APOPHYLLITES

MINERAL:

FORMULA:

SYMMETRY:

COLOR

RANGE:

TYPE LOCALI

TY:

FLUORESCENCE:

FLUOR- APOPHYL

LITE

(K, Na)Ca4

Si8O20(F,OH) - 8H2O

Tetragonal;

4/m 2/m 2/m

White, colorle

ss, green, yellow

or violet

Not named

Some specimens fluoresce

pale green or yellow

HYDROXY-

APOPHYLLITE

KCa4 Si8O20(OH, F) - 8H2O

Tetragonal;

4/m 2/m 2/m

White or

colorless

Ore Knob Mine,

Jefferson, North Carolina

Non-fluorescent

NATRO- APOPHYL

LITE

NaCa4 Si8O20F -

8H2O

Orthorhombic;

2/m 2/m 2/m

(pseudo- tetragona

l)

brown,

brownish

yellow,

yellow or

colorless

Sampo Mine,

Takahashi,

Okayama,

Honshu, Japan

Non-fluorescent

Fluorapophyllite is by far the most abundant and colorful of the three and is usually what is referred to when a specimen is just labeled apophyllite. Hydroxyapophyllite is also relatively common, but specimens typically lack any color and are limited to pseudo-cubic crystal habits. The natroapophyllite is quite rare and is found at only a few localities. Its typical brown color can help distinguish it from its close cousins. Natroapophyllite, by virtue of its more significant chemical and symmetrical difference, is truly a distinct mineral. Fluorapophyllite and hydroxyapophyllite however are a different story. The two are different minerals only because of the difference in the percentage of fluorine to hydroxyl ions. They represent the end members of a series that could be called the apophyllite series. The name apophyllite persists however and its usage is widespread especially when distinguishing the true identity of specimens is difficult. Most mineral guide books list only apophyllite as a single mineral and the rest of this discussion will deal with apophyllite in general. Apophyllite is often thought of as a Zeolite Group mineral. But this would be wrong ! Zeolites are network silicates belonging to the Tectosilicate Subclass whereas apophyllite is a layered Phyllosilicate.The structural differences aside, apophyllite

does have a lot of similar properties to many of the zeolite minerals. Chief among them is its low specific gravity, environment of formation and ability to lose water when heated (although it does not have the ability to re-absorb the water like zeolites). What confuses the issue is how common apophyllite and zeolites are associated together in low temperature/low pressure metamorphic environments. This is fortunate for mineral collectors as there are few mineral combinations that can beat the awesome apophyllite, stilbite, heulandite and natrolite specimens for sheer aesthetic beauty!

Another typically associated mineral is the green translucent prehnite that forms a rolling carpet on top of which are scattered sparkling clear pseudo-cubic apophyllite crystals,

making very attractive specimens. Kinoite from the Christmas Mine in Arizona is a beautiful blue color and is often coated in tiny sparkling apophyllite crystals. Apophyllite is commonly associated with exceptional quartz and calcite crystals as well. Its wonderful associations are nice, but apophyllite is more often then not the star attraction. What makes apophyllite so popular among collectors is its fantastic crystals with their gem-like vitreous to pearly luster. Apophyllite almost always forms good crystals of two major types. The favorite crystal habit is the rectangular prism capped by a steep four sided pyramid (tetragonal dipyramid). A doubly terminated crystal is exceptionally special. The faces of the pyramids are rotated 45 degrees with respect to the prism faces and so plunge down into the prism edges. This produces a diamond-shaped pyramidal face instead of a typical triangular pyramid face such as on quartz. The shape is an extraordinary example of tetragonal crystal form. Although normally colorless or white, colored examples of apophyllite are always treasured. By far its most impressive color is the pastel green color that augments specimens from Poona, India. Some crystals of apophyllite are cut as gems, but mostly just for collectors. The other common crystal habit is a pseudo-cubic crystal that occurs when there is no pyramid and the prism is ended by a flat termination (a pinacoid). The pinacoid is a crystal form that is perpendicular to the length of the crystal and so can abruptly terminate the prism. It is often seen as simply truncating the pyramids by cutting off the points of the crystal. When the prism is short and blocky and there is no pyramidal faces, then the pinacoid face can make the crystal appear cube shaped. However the prism faces are commonly striated and all in one direction while the pinacoid is smooth, giving its true symmetry away. Conversely, if the pyramid faces are the only dominant form then the crystal can fool someone in to thinking it is octahedral! Apophyllite specimens are found in ancient lava and basalt flows. The crystals grow in the now solid cavities, called

amygdules or vesicles, formed by air bubbles when the rock was molten. Apophyllite is also found in the voids in the contact metamorphic zone limestones that surround intrusive rocks. Apophyllite lends it name to a small group of minerals called the Apophyllite Group which includes, in addition to

fluorapophyllite, hydroxyapophyllite and natroapophyllite, the mineral carletonite with a formula of KNa4Ca4(CO3)4Si8O18 (F, OH) - H2O. The Apophyllite Group is structurally very interesting. Like other members of the Phyllosilicates Subclass, the Apophyllite Group's structure is layered with alternating silicate sheets and the potassium, sodium, calcium, fluorine and water layers. But unlike other phyllosilicates, the Apophyllite Group silicate sheets are composed of interconnected four and eight-member rings. The sheets can be thought of as being like chicken wire with alternating octagon and square shaped holes. Both octagons and squares have a four fold symmetry and this is what gives these minerals their typical tetragonal or pseudo-tetragonal symmetry. Only Apophyllite Group members have this unique interconnected four and eight-member ring structure. THE PHYSICAL CHARACTERISTICS OF APOPHYLLITE:

Color is clear, white, green, yellow, pink, violet or rarely

brown.

Luster is vitreous to pearly on cleavage surfaces.

Transparency: Crystals are transparent to translucent.

Crystal System is tetragonal; 4/m 2/m 2/m; natroapophyllite is orthorhombic, 2/m 2/m 2/m.

Crystal Habits include four sided prisms (with a square cross-section) truncated with either a steep four sided pyramid or a pinacoid termination or both. If the pyramids are missing, the crystals can look cubic. Rarely are the prisms missing, but if they are, crystals could appear octahedral because of the four sided pyramids. The faces of the pyramids do not lineup with the prism faces but with their edges, therefore the

pyramid faces have four edges and appear diamond shaped instead of triangular like the pyramid faces of quartz. Rare tabular hydroxyapophyllite crystals are

also known.

Cleavage is perfect in one direction (basal).

Fracture is uneven.

Hardness is 4.5 - 5.

Specific Gravity is approximately 2.3 - 2.4 (lighter than

most translucent minerals).

Streak is white.

Other Characteristics: Prism faces are striated

lengthwise, some specimens are fluorescent and crystals will flake when heated.

Associated Minerals are prehnite, quartz, heulandite, stilbite, natrolite, analcime, datolite, babingtonite, cavansite, calcite, idocrase, wollastonite, kinoite, gyrolite and many other zeolites.

Notable Occurrences are extensive and include the

Deccan Traps (ancient basalt flows) in India especially around Poona, also found in Christmas Mine, Arizona;

Fairfax, Virginia; Upper Peninsula, Michigan; Oregon; Pennsylvania; Paterson, New Jersey and North Carolina, USA; Rio Grande do Sul, Brazil; Isle of Skye, Scotland; Collinward, Northern Ireland; Mexico; Nova Scotia and Mont Saint-Hilaire, Canada; Iceland; Kongsberg, Norway; Harz Mountains, Germany and

Sampo Mine, Takahashi, Okayama, Honshu, Japan.

Best Field Indicators are crystal habit, striations,

associations, environment of formation, cleavage and luster on cleavage surfaces.

AQUAMARINE, THE BLUE VARIETY OF BERYL

VARIETY INFORMATION:

VARIETY OF: Beryl , Be3 Al2 Si6 O18 .

USES: Gemstone.

BIRTHSTONE FOR: March

COLOR: various shades of blue to blue-green.

INDEX OF REFRACTION: 1.57 - 1.60

BIREFRINGENCE: 0.004 - 0.008

HARDNESS: 7.5 - 8

CLEAVAGE: one direction, poor.

CRYSTAL SYSTEM: hexagonal

Pleochroic: weak

For natural aquamarine mineral specimens see our For Sale or Sold lists

Aquamarine is the blue, or perhaps more correctly, blue-green or aqua variety of the mineral beryl. Other gemstone color varieties that belong to beryl include emerald, morganite, and heliodor. Other colors of beryl are simply refered to by their color, such as red beryl. Aquamarine is colored by trace amounts of iron that find their way into the crystal structure. Most gem aquamarines have been heat treated to produce the popular blue-green colors from less desirable yellow or pale stones. The leading producer of aquamarines is the country of Brazil, which has many mines. Pakistan, as well as many U.S. localities, produce wonderful specimens as well.

THE MINERAL ARAGONITE

Chemistry: CaCO3, Calcium Carbonate

Class: Carbonates

Group: Aragonite

Uses: minor constituent of limestone which is used in cement and in steel production, ornamental carvings and as mineral specimens.

Specimens

Aragonite is a common carbonate mineral. It is unfortunately often thought of as the poor cousin to calcite. But aragonite is an interesting and attractive mineral in its own right. It forms interesting habits and can have a soft pretty color. Its modes of formation and relationship to calcite are both curious and intriguing. Aragonite is a polymorph of calcite, which means that it has the same chemistry as calcite but it has a different structure, and more importantly, different symmetry and crystal shapes. Aragonite's more compact structure is composed of triangular carbonate ion groups (CO3), with a carbon at the center of the triangle and the three oxygens at each corner. Unlike in calcite, the carbonate ions do not lie in a single plane pointing in the same direction. Instead they lie in two planes that point in opposite directions; destroying the trigonal symmetry that is characteristic of calcite's structure. To illustrate this, imagine the symmetry of an equilateral triangle; a three fold rotation with three mirror planes that cross in the center. Now join two of these triangles together at their bases and you have a diamond-shaped figure with the symmetry of a two fold rotation with one mirror plane in the middle. This is what the effect of the two carbonate planes with opposite orientations has on the symmetry of this structure. Aragonite has an orthorhombic symmetry (2/m 2/m 2/m) instead of calcite's "higher" trigonal (bar 3 2/m) symmetry. A very rare mineral called vaterite is

also a polymorph of aragonite and calcite; making them all trimorphs. Vaterite has an hexagonal symmetry (6/m 2/m 2/m). Carbonate minerals with this same structure as aragonite belong to the Aragonite Group of minerals. The structure is

responsible for the similar properties of this group. Dissimilar properties are the responsibility or result of the differing metal cations in the various minerals of the group. Aragonite is technically unstable at normal surface temperatures and pressures. It is stable at higher pressures, but not at higher temperatures such that in order to keep aragonite stable with increasing temperature, the pressure must also increase. If aragonite is heated to 400 degrees C, it will spontaneously convert to calcite if the pressure is not also increased. Since calcite is the more stable mineral, why does aragonite even form? Well under certain conditions of formation, the crystallization of calcite is somehow discouraged and aragonite will form instead. The magnesium and salt content of the crystallizing fluid, the turbidity of the fluid and the time of crystallization are decidedly important factors, but there are perhaps others. Such areas as sabkhas and oolitic shoals tend to allow significant amounts of aragonite to form. Also metamorphism that includes high pressures and low temperatures (relatively) can form aragonite. After burial, given enough time, the aragonite will almost certainly alter to calcite. Sedimentologists are very interested in aragonite and calcite stability fields because the conversion of aragonite to calcite after deposition has a distinct effect on the character of the sedimentary rocks. Aragonite's most famous crystal habit is the twinned pseudo-hexagonal prismatic crystals that it produces. Twinning is the

result of an error during the growth of the crystal. It occurs when the atomic layer stacking, in a sequence such as ABCABCABCABCABCABC etc, makes a mistake and a C layer instead of a B layer is place next to an A layer. The result

is an ABCABCABCACBACBACBA stacking sequence (can

you pick out the mistake?). Where the mistake occurs, a mirror plane is produced that was not there before (the left side is the mirror image of the right side). This has the effect of increasing the apparent symmetry of the crystal. The error in aragonite's structure causes a bend in the crystal of exactly 120 degrees. If three bends or twins occur, then a 360 degree crystal, called a cyclic twin or trilling, can form. In this case, aragonite can appear hexagonal (six sided). These crystals can be thought of as a "triple siamese twin" where one crystal takes up one third (or 120 degrees) of a hexagon. Individual cyclic twins from Aragon, Spain have been popular but are being surpassed by the amazing clusters of aragonite twins that are now available from Morocco in large numbers. Aragon, Spain is where aragonite was first discovered and from where aragonite gets its name. Cyclic twins often show notches that separate the twin individuals. Aragonite also has another popular habit called flos ferri or "flowers of iron". This is a branching, clumpy habit that can make delicate tree, coral or worm-like formations that are most unique. A steep pyramidal habit forms clusters of sharp spiked crystals sometimes referred to as a "church steeple" habit. Aragonite is a constituent of many sea creatures' shell structures; a curious development since calcite is the more stable form of calcium carbonate. Most bivalve animals and corals secrete aragonite for their shells and pearls are composed of mostly aragonite. The pearlization and iridescent colors in sea shells such as abalone are made possible by several minute layers of aragonite. Other environments of formation include hot springs deposits, cavities in volcanic rocks, caves and mines. PHYSICAL CHARACTERISTICS:

Color can be white or colorless or with usually subdued

shades of red, yellow, orange, brown, green and even blue.

Luster is vitreous to dull.

Transparency: Crystals are transparent to translucent.

Crystal System is orthorhombic; 2/m 2/m 2/m

Crystal Habits include twinned hexagonal prismatic

crystals as well as a diverse assortment of thin elongated prismatic, curved bladed, steep pyramidal (spiked) and chisel shaped crystals. A branching tree, coral or worm-like delicate form is called "flos ferri".

Can also be compact, granular, radially fibrous and massive. Its massive forms can be layered, coralloid, pisolitic, oolitic, globular, stalachtitic and encrusting. Aragonite is a constituent of many species' shell structures. A layered sedimentary marble like formation is called Mexican Onyx and is used for carvings and ornamental purposes. Calcite pseudomorphs of aragonite crystals and formations are common.

Cleavage is distinct in one direction (pinacoidal).

Fracture is subconchoidal.

Hardness is 3.5-4

Specific Gravity is 2.9+ (average for non-metallic

minerals)

Streak is white.

Other Characteristics: aragonite effervesces easily in

cold dilute hydrochloric acid, is strongly birefringent, is fluorescent and its refractive index is 1.7 .

Associated Minerals include gypsum, barite, smithsonite, malachite, calcite, serpentine, sulfur, celestite, zeolites, quartz, clays, dolomite, limonite, chalcopyrite and wulfenite among many others.

Notable Occurrences include Aragon, Spain (its type

locality and from where it gets its name); Morocco; Bastennes, France; Girgenti, Sicily; Alston Moor and Cleator Moor, Cumberland, England; Baja California, Mexico (Mexican Onyx); Tsumeb, Namibia; Carinthia,

Austria; Leadhills, Scotland; Harz Mountains, Germany

and in several localities in the Southwestern United States.

Best Field Indicators are crystal habits, single plane

of cleavage and reaction to acid.

THE MINERAL ARGYRODITE

Chemistry: Ag8GeS6, Silver Germanium Sulfide.

Class: Sulfides.

Uses: As mineral specimens and as a very minor ore of silver.

Specimens

Argyrodite is a rare silver germanium sulfide mineral. It was first discovered in the silver mining area of Freiberg, Saxony,

Germany in the Himmelsfurst Mine. When it was discovered, the element germanium was only theorized to exist by Mendeleev in 1871. Fifteen years later, the element is discovered in samples of a new mineral species, argyrodite! Germanium was named for Germany and is an important element in semiconductors, special optical glass and medicine. Argyrodite is not an ore of germanium due to its rarity and the fact that sufficient germanium is recovered from the burning of coal and the refining of zinc ores in which it is found as a trace element. There are only about 20 minerals that consistently contain germanium of which the more common are the sulfides argyrodite, germanite and renierite. Argyrodite gets its name from the Greek words that loosely translate into "rich in silver".

Argyrodite forms a series with the mineral canfieldite; Ag8SnS6. Notice the difference in formula? The germanium ion, Ge, in argyrodite has been replaced by a tin ion, Sn, in canfieldite. A series is where two or more minerals show substitution with one or more elements in their chemistries, but the structure is essentially the same. Both these minerals have been classified as sulfosalts, but this is not universally accepted. PHYSICAL CHARACTERISTICS:

Color is a steel gray to reddish gray; tarnishes to black.

Luster is metallic.

Transparency: Crystals are opaque.

Crystal System: Orthorhombic (pseudo-isometric); m

m 2.

Crystal Habits include pyramidal (pseudo-octahedral)

and pseudo-dodecahedral crystals and botryoidal crusts and massive forms.

Cleavage: None.

Fracture: Conchoidal.

Hardness is 2.5

Specific Gravity is 6.2 - 6.5 (heavier than average for

metallic minerals)

Streak is gray.

Notable Occurrences are limited to the type locality of Himmelsfurst Mine, Freiberg, Saxony, Germany as

well as Oruro, Bolivia.

Associated Minerals include acanthite, pyrite and other sulfides.

Best Field Indicators are crystal habit, locality, color, lack of cleavage and density.

THE MINERAL NATIVE ARSENIC

Chemistry: As, Elemental Arsenic

Class: Elements

Group: Arsenic

Uses: A very minor ore of arsenic and as mineral specimens.

Specimens

Arsenic is historically the poison of choice for many murders, in reality and in fiction. Here, arsenic is dealt with only as mineral specimens and is not to be ingested. Although it has been used as a poison, arsenic has many chemical uses and is quite an important element. Arsenic does not often form in its elemental state and is far more common in sulfides and sulfosalts such as arsenopyrite, orpiment, realgar, lollingite and tennantite. Due to the abundance of these arsenic bearing ores and the rarity of native arsenic, it is not an important ore of itself. Native arsenic is found in silver ore veins and is processed along with the silver ore and is therefore is a minor source of arsenic. Native arsenic is usually found to have a trigonal symmetry but a very rare orthorhombic arsenic is known from Saxony, Germany and is named arsenolamprite. The two minerals are

called polymorphs (many shapes) because they have the same chemistry, As, but different structures. An obscure variety name for the concentrically banded or "shelly" arsenic is "scherbencobalt". Some arsenic will have

some antimony in its structure and native antimony is nearly

indistinguishable from arsenic. PHYSICAL CHARACTERISTICS:

Color is tin-white which quickly tarnishes to dark gray

or black.

Luster is metallic but the tarnish will often dull the luster dramatically.

Transparency: Crystals are opaque.

Crystal System is trigonal; bar 3 2/m

Crystal Habits include rare pseudocubic rhombohedral

crystals and acicular radial aggregates. More commonly found in fine grained masses with concentric bands or botryoidal crusts.

Cleavage is perfect in one direction (basal), but rarely

visible.

Fracture is uneven.

Hardness is 3 - 4

Specific Gravity is 5.4 - 5.9+ (somewhat heavy for a

metallic mineral)

Streak is black.

Associated Minerals include silver, dyscrasite, barite, cinnabar and nickeline.

Other Characteristics: Will often have a garlic odor

and is poisonous.

Notable Natural Occurrences include Vosges,

France; Kongsberg, Norway; Saxony and Harz Mountains, Germany; Honshu, Japan; England; Italy and Santa Cruz Co., Arizona and New Jersey, USA.

Best Field Indicators are tarnish, density, softness,

crystal habits, color, garlic smell and associations.

THE MINERAL ARSENOPYRITE

Chemistry: FeAsS, Iron Arsenide Sulfide

Class: Sulfides and Sulfosalts

Group: Arsenopyrite Group

Uses: Important ore of arsenic, minor source of gold and as mineral specimens.

Specimens

A major ore of arsenic, Arsenopyite can contain a small amount of gold as an impurity. Although an ore of arsenic, it is not intentionally mined for that reason. In processing the ore of other elements some arsenopyrite is "accidentally" included and gives off its arsenic as fumes that are then recovered. This "accidental" source supplies most of the world's needs in arsenic. Arsenopyrite makes attractive mineral specimens as well. It's well formed crsytals show a distinct and interesting crystal form. A typical crystal contains a diamond shaped dome atop a prismatic crystal. The crystals have sharp acute angles that are a marked contrast from other sulfides that generally have only obtuse angles. PHYSICAL CHARACTERISTICS:

Color is a brassy white to gray.

Luster is metallic.

Transparency: Crystals are opaque.

Crystal System is orthorhombic; 2/m 2/m 2/m

Crystal Habits include prismatic crystals with a

diamond cross section terminated by either a steep

dome (actually two of the four faces of a prism) or a less inclined dome, also short stubby crystals doubly terminated with domes. Twinning is common, often

bending the crystal and sometimes forming crosses, x's or stars.

Cleavage is distinct in two directions forming prisms.

Fracture is uneven.

Hardness is 5.5 - 6.

Specific Gravity is approximately 6.1+ (heavier than

average for metallic minerals)

Streak is dark gray to black

Other Characteristics: Striations on dome faces, bitter smell when powdered or broken.

Associated Minerals are gold, siderite, pyrite and

other sulfides.

Notable Occurrences include Kyushu Island and

Iname, Japan; Cornwall, England; Bolivia; Freiberg, Germany; Wawa area of Ontario, Canada and Valais, Switzerland.

Best Field Indicators are crystal habit, cleavage, smell when struck, color and luster.

THE MINERAL ARSENTSUMEBITE

Chemistry: Pb2Cu(AsO4)(SO4)OH , Lead Copper Arsenate Sulfate Hydroxide

Class: Phosphates

Subclass: Arsenates

Uses: only as a mineral specimen.

Specimens

Arsentsumebite forms good, colorful specimens and is a popular collection mineral, although quite rare. It is closely related to its cousin, tsumebite. The two minerals are in a series in which the arsenate ion group in arsentsumebite is replaced by a phosphate ion group in tsumebite. The two differ only slightly; this is mostly because the structure is the same in the two minerals. Both are formed in the oxidation zone of lead-copper ore deposits. Both minerals are unusual in that they have two ion groups instead of the usual one in most minerals. It the case of arsentsumebite, it has an arsenate ion group and a sulfate ion group. Mineralogists prefer to classify it as a phosphate (where

arsenates are placed) because the arsenate ion group has a higher negative charge (-3) than the sulfate group (-2). PHYSICAL CHARACTERISTICS:

Color is green.

Luster is vitreous.

Transparency crystals are transparent to translucent.

Crystal System is monoclinic.

Crystal Habits include tabular crystals that can form twinned trillings and also as crusts.

Cleavage: None.

Fracture: Uneven.

Hardness is 3

Specific Gravity is approximately 6.4 (heavy for

translucent minerals)

Streak is green.

Associated Minerals include azurite, cerussite and smithsonite.

Notable Occurrences are limited to Tsumeb, Namibia

and a few other sites.

Best Field Indicators are crystal habit, locality,

associations, density and color.

THE MINERAL ARTHURITE

Chemistry: CuFe2(AsO4, PO4, SO4)2 - 4H2O, Hydrated Copper Iron Arsenate Phosphate Sulfate Hydroxide

Class: PhosphateClass

Subclass: Arsenates

Group: Arthurite

Uses: Only as mineral specimens.

Specimens

Arthurite is a rare copper iron arsenate. It is typically green and forms small acicular crystals. Specimens from the classic mines of Cornwall, England are often associated with other rare minerals such as pharmacosiderite and beudantite, and

these specimens are much sought after. Arthurite is unusual in that it contains a variety of anions, namely arsenate, phosphate

and sulfate. Percentage whys, the arsenate anion dominates in natural specimens, but all anions are usually present in the same specimen. Arthurite lends its name to a small group of rather obscure minerals called the Arthurite Group. The Arthurite Group is a

group of monoclinic, hydrated iron arsenates and phosphates with a general formula of XFe2(AO4)2(O, OH)2 - 2H2O The X

in the formula can be either copper, iron, manganese and/or zinc. The A in the formula can be either arsenic or

phosphorous. These are the members of the Arthurite Group:

Arthurite (Hydrated Copper Iron Arsenate Phosphate

Sulfate Hydroxide)

Earlshannonite (Hydrated Manganese Iron Phosphate Hydroxide)

Ojuelaite (Hydrated Zinc Iron Arsenate Hydroxide)

Whitmoreite (Hydrated Iron Phosphate Hydroxide) PHYSICAL CHARACTERISTICS:

Color is apple green to emerald green.

Luster is vitreous to pearly.

Transparency: Crystals are translucent.

Crystal System is monoclinic.

Crystal Habits include prismatic to acicular crystals

and globular aggregates and crusts.

Cleavage is not observed.

Fracture is uneven.

Hardness is 3 - 4

Specific Gravity is approximately 3.0 - 3.2 (average

for translucent minerals).

Streak is green.

Associated Minerals are pharmacosiderite, beudantite and other secondary arsenate minerals.

Notable Occurrences include Calstock, Cornwall,

England; Atacama Province, Chile and Majuba Hill, Nevada, USA.

Best Field Indicators are color, crystal habit, streak

and associations.

THE MINERAL ARTINITE

Chemistry: Mg2CO3(OH)2 - 3H2O , Hydrated Magnesium Carbonate Hydroxide.

Class: Carbonates

Uses: Only as mineral specimens.

Specimens

Artinite is a somewhat rare carbonate mineral. It forms as a crust of acicular to fibrous crystal aggregates sometimes collected into tight perfectly spherical balls. It is always associated with ultra-basic igneous and metamorphic rocks such as serpentinite. It often surprises people when they are told that it is a carbonate mineral. It has the appearance of several silicate minerals and forms in a somewhat atypical carbonate environment. It has nearly the same habit as mesolite, pectolite, natrolite, okenite and gyrolite. However these minerals are not associated with the mineral serpentine like artinite. In fact a specimen of artinite without serpentine would be very unusual. The two minerals make for a nice association

couple. They are popular and attractive with the snow white fibrous balls of artinite set upon the greasy lustered jade green serpentine base. PHYSICAL CHARACTERISTICS:

Color is white or colorless.

Luster is silky to fibrous.

Transparency crystals are transparent to translucent.

Crystal System is monoclinic; 2/m

Crystal Habits include radiating spherical aggregates

of acicular to fibrous crystals.

Hardness is 2.5

Specific Gravity is 2.0 (very light)

Cleavage is perfect in one direction.

Fracture is fibrous.

Streak is white.

Associated Minerals include serpentine, hydromagnesite, talc and olivine.

Notable Occurrences include San Benito Co.,

California and Long Island, New York, USA and Campo Franscia, Lombardia, Italy.

Best Field Indicators are crystal habits, color,

associations, softness and density.

THE MINERAL ASTROPHYLLITE

Chemistry: (K,Na)3(Fe,Mn)7Ti2(SiO3)8(O,OH)7, Potassium Sodium Iron Manganese Titanium Silicate Hydroxide.

Class: Silicates

Subclass: Inosilicates

Group: Astrophyllite

Uses: mineral specimen

Specimens

Astrophyllite is a rare titanium mineral found in some unusual granites and syenites. It produces a variable luster that can be nearly metallic in one specimen to vitreous in another. Its name translated means star sheets and probably is in allusion to the intergrown starlike aggregates that it can form. PHYSICAL CHARACTERISTICS:

Color is usually golden yellow or yellowish brown, but also greenish brown specimens are found.

Luster is vitreous or submetallic to metallic, can be

pearly on cleavage surfaces.

Transparency: crystals are translucent to opaque.

Crystal System is triclinic; bar 1

Crystal Habits include small tabular or bladed crystals

often grouped in starlike aggregates. Also found in lamellar massives.

Cleavage is perfect in one direction.

Fracture is uneven.

Hardness is 3.

Specific Gravity is 3.3 - 3.4

Streak is yellowish white.

Associated Minerals are quartz, feldspars, nepheline, micas and aegirine.

Other Characteristics: color is often patchy or heterogenous in distribution.

Notable Occurrences include Kola Penensula,

Khibina, Russia; Colorado, USA and Mt St. Hilaire, Quebec, Canada.

Best Field Indicators brittleness, cleavage, color,

luster and localities.

THE MINERAL ATACAMITE

Chemistry: Cu2Cl(OH)3, Copper Chloride Hydroxide.

Class: Halides

Subclass: Oxy-halides

Uses: as a minor ore of copper and as mineral specimens.

Specimens

Atacamite is an unusual and attractive halide mineral. It is polymorphous with two other minerals; paratacamite and botallackite. A polymorph is a mineral that shares the same

chemistry with other minerals but has a different crystal structure. These three minerals are members of the Oxy-halides Subclass. This subclass of the halide minerals is unique in possessing oxygens and hydroxides in their chemistries. Atacamite forms in arid climates where copper minerals are exposed to oxidation. The Atacama Desert, from where atacamite gets its name, is one of the driest places in the world. Atacamite has a deep green color and is often associated with many other rare and colorful minerals such as chyrsocolla, brochantite, pseudomalachite, connellite, linarite,

caledonite, libethenite, cornetite, cuprite and malachite.

Some of these specimens can be quite beautiful, with a combination of blue, green, and red hues. Atacamite is a wonderful and interesting addition to someones collect. PHYSICAL CHARACTERISTICS:

Color is dark green.

Luster is vitreous.

Transparency: Crystals are transparent to translucent.

Crystal System is Orthorhombic; 2/m2/m2/m

Crystal Habits include slender striated crystals that

can be accicular to fiberous.

Cleavage is perfect in one direction.

Fracture is splintery.

Hardness is 3 - 3.5

Specific Gravity is approximately 3.75+ (above average)

Streak is pale green.

Associated Minerals include limonite, chyrsocolla, brochantite, pseudomalachite, connellite, linarite, caledonite, libethenite, cornetite, cuprite and malachite.

Other Characteristics: crystals are vertically striated.

Notable Occurrences include Atacama Desert, Chile; Mt. Vesuvius, Italy; Wallaroo, Australia; Mexico and Pinal County, Arizona, USA.

Best Field Indicators are crystal habit, color,

associations and localities.

THE MINERAL AUGELITE

Chemistry: Al2PO4(OH)3, Aluminum Phosphate Hydroxide.

Class: Phosphates

Uses: Only as mineral specimens.

Specimens

Augelite is not a well known phosphate mineral. It is difficult to recognize, especially when found as clear and colorless tiny crystals. Augelite is found in granitic pegmatites, but mostly in hydrothermal veins. The best locality for good crystals is White Mountain, Mono County, California. Up until that discovery, augelite was only known as tiny crystals and cleavage masses. PHYSICAL CHARACTERISTICS:

Color is usually colorless, white or pale shades of

yellow, blue, pink or rose.

Luster is vitreous.

Transparency: Specimens are transparent to

translucent.

Crystal System is monoclinic; 2/m

Crystal Habits include tiny to microscopic tabular or

platy crystals with an overall triangular aspect or larger equant complex crystals and found massive.

Cleavage is good in two directions.

Fracture is conchoidal.

Hardness is 4.5 - 5.

Specific Gravity is approximately 2.7 (average).

Streak is white.

Associated Minerals include andalusite, lithiophilite and triphylite and other phosphates.

Notable Occurrences include the Vestana Mine,

Nastum, Skane Sweden; Oruro, Bolivia; Rapid Creek, Yukon Territory, Canada; White Picacho district, Arizona; North Groton, New Hampshire; in the Black Hills region of South Dakota and especially at White Mountain, Mono County, California, USA.

Best Field Indicators are crystal habit, color,

associations, localities and cleavage.

THE MINERAL AUGITE

Chemistry: (Ca, Na)(Mg, Fe, Al)(Al, Si)2 O6, Calcium Sodium Magnesium Iron Aluminum Silicate.

Class: Silicates

Subclass: Inosilicates

Group: Pyroxenes

Uses: only as mineral specimens.

Specimens

Augite is an important rock-forming mineral in many igneous rocks, especially in gabbros and basalts, and is also found in some hydrothermal metamorphic rocks. Augite is a part of an important solid solution series of the pyroxene group. The series includes the minerals hedenbergite, CaFeSi2 O6, and

diopside , CaMgSi2 O6. A series occurs when ions (in this

case iron and magnesium) can freely substitute between each other. Augite is the intermediate member of the series. However, augite is not just an intermediate, but is unique in that it contains percentages of sodium and aluminum that are mostly lacking in diopside and hedenbergite. The magnesium content is also larger in augite than in either of the other two minerals. The diopside-hedenbergite series is analogous to amphibole's tremolite- actinolite series.

Mineral specimens of augite, while ordinarily unattractive and not very interesting, can have some specimens that are very striking in appearance and are of interest to many mineral collectors. Its name is derived from the greek word augites which means "brightness" in allusion to its relatively high luster that is seen on some exceptional specimens. PHYSICAL CHARACTERISTICS:

Color is dark green, brown and black

Luster is vitreous to submetallic and even dull.

Transparency crystals are transparent to mostly

translucent or opaque.

Crystal System is monoclinic; 2/m

Crystal Habits include short prismatic, rarely tabular

crystals. The square cross section is distinctive in the prismatic crystals. Also compact, granular, columnar, lamellar and fibrous(rare).

Cleavage is perfect in two lengthwise directions at

close to right angles.

Fracture is uneven.

Hardness is 5 - 6

Specific Gravity is approximately 3.2 - 3.6 (slightly above average)

Streak is greenish white.

Other Characteristics: The basal parting is prominent.

Associated Minerals are olivine, biotite, nepheline, albite, apatite, serpentine, leucite and hornblende.

Notable Occurrences include Grand Co, Colorado, St. Lawrence Co., New York and Tillamook, Oregon, USA; Eifel, Germany; Mt. Vesuvius, Italy; France and the Bohemian regions of Europe.

Best Field Indicators are crystal habit, associations,

color, parting and cleavage.

THE MINERAL AURICHALCITE

Chemistry: (Zn, Cu)5(CO3)2(OH)6, Zinc Copper Carbonate Hydroxide

Class: Carbonates

Uses: very minor ore of zinc and copper and as a mineral specimen

Specimens

Aurichalcite forms in the oxidation zones of zinc-copper deposits. Crystals are acicular or fibrous and found in tufted aggregates. The color is an attractive grass green to pale green. Aurichalcite will at times partially cover red limonite and be associated with such colorful minerals as azurite, smithsonite and malachite. Specimens of aurichalcite certainly make for colorful "landscape" specimens. Aurichalcite can be confused with Rosasite, (Cu, Zn)2CO3(OH)2. However rosasite is usually more massive but not lamellar. Rosasite crystals are harder than aurichalcite; 4 vs 1 - 2, respectively.

PHYSICAL CHARACTERISTICS:

Color is usually a grass green but varies from white to

green to greenish blue to light blue.

Luster is silky to fibrous or pearly on more massive specimens.

Transparency crystals are transparent to translucent.

Crystal System is orthorhombic; 2 2 2

Crystal Habits include radiating tufts of acicular

crystals. also encrustations of fiberous or lamellar masses.

Hardness is 1 - 2

Specific Gravity is 3.6 - 4 (above average for non-

metallic minerals)

Cleavage is perfect in one direction.

Fracture is uneven or fiberous.

Streak is white to pale shades that depend on color.

Associated Minerals include limonite, smithsonite, azurite, malachite, rosasite and calcite.

Other Characteristics: effervesceses easily in cold

dilute hydrochloric acid.

Notable Occurrences include Bisbee, Arizona;

Laurium, Greece; Tsumeb, Namibia and Mapimi, Durango, Mexico.

Best Field Indicators are crystal habits, color,

associations, softness and reaction to acid.

THE MINERAL AUSTINITE

Chemistry: CaZnAsO4OH, Calcium Zinc Arsenate Hydroxide

Class: The Phosphates

Subclass: Arsenates

Group: Adelite

Uses: Only as mineral specimens.

Specimens

Austinite is fairly rare but popular collection mineral. It forms in the oxidation zone of zinc ore deposits, often with the sometimes similar looking adamite. It can have a very nice

color and silky or sub-adamantine (almost gem-like) luster. Austinite is named after the mineralogist Austin F. Rogers. PHYSICAL CHARACTERISTICS:

Color is typically a bright green, but also colorless,

white or pale yellow.

Luster is sub-adamantine or silky.

Transparency: Crystals are transparent to translucent.

Crystal System is orthorhombic; 2/m 2/m 2/m

Crystal Habits include acicular or bladed crystals in

druses, radial aggregates or crusts, also fibrous.

Cleavage is perfect in one direction lengthwise.

Fracture is uneven.

Hardness is 4 - 4.5.

Specific Gravity is approximately 4.1 (heavy for

translucent minerals)

Streak is white to pale green.

Associated Minerals are adamite, legrandite, limonite, smithsonite, aragonite and other oxidation zone minerals.

Notable Occurrences include Mapimi, Mexico;

Tsumeb, Namibia and Toole Co., Utah, USA.

Best Field Indicators are crystal habit, cleavage,

color, luster, density, lack of fluorescence and associations.

THE MINERAL AUTUNITE

Chemistry: Ca(UO2)2(PO4)2-10H2O , Hydrated Calcium Uranyl Phosphate.

Class: Phosphates

Group: Autunite/Torbernite

Uses: a minor ore of uranium and mineral specimens

Specimens

Autunite is one of the more attractive and popular radioactive minerals. To state the obvious, the uranium in its chemical formula provides this radioactivity. Autunite is probably the most popular uranium mineral for collectors. Its green and yellow color shades seem to glow and are actually fluorescent. The crystal aggregates look like inflated mica books and are very distinctive. The structure is composed of phosphate tetrahedrons linked to uranium-oxygen groups that form distorted octahedrons. The phosphates and uranium groups lie in sheets that are weakly held together by water molecules. This structure produces the

tabular habit, the one perfect direction of cleavage, and the relative softness. Autunite can lose water and convert to a different mineral called meta-autunite-I of the meta-autunite/meta-torbernite group of minerals and with heating can produce a meta-autunite-II mineral. Oddly, neither mineral is found in nature in any appreciable abundance. However, the conversion is irreversible and ongoing, and all collection specimens of a certain age are at least partially converted. Eventually after many years the meta-autunite will powder, and the specimen will be ruined. Fine autunite specimens should be stored in a closed container to avoid water loss. Some drastic measures have been attempted on fine museum quality specimens to thwart the conversion to meta-autunite, including lacquering. Remember, this is also a radioactive mineral and should be stored away from other minerals that are affected by radioactivity, and human exposure should be limited. PHYSICAL CHARACTERISTICS:

Colors are various shades of dark green to bright

"lemon" yellow, often with a mixture of yellow and green shades in one specimen.

Luster is vitreous to pearly on the main pinacoid.

Transparency crystals are translucent to opaque.

Crystal System is tetragonal; 4/m 2/m 2/m

Crystal Habits include tabular square crystals

dominated by two pinacoid faces. Crystals are often in parallel growths that can have a "fanned-out" look or in rosetta clusters. Also as crusts, earthy masses, foliated and scaly aggregates.

Cleavage is perfect in one direction.

Fracture is uneven.

Hardness is 2 - 2.5

Specific Gravity is approximately 3.1 - 3.2 (slightly above average for translucent minerals)

Streak is yellow.

Associated Minerals are torbernite, meta-torbernite, uranocircite, uranophane, uraninite and other

uranium minerals.

Other Characteristics: fluorescent yellow-green,

radioactive, somewhat pleochroic and thin crystals or cleavage sheets are bendable.

Notable Occurences include Autun, France; Cornwall,

England; Mitchell Co., North Carolina and Mt. Spokane, Washington, USA; Zaire; Bergen, Germany and Portugal.

Best Field Indicators are color, crystal habit,

fluorescence, radioactivity, associations and flexible crystals.

THE MINERAL AXINITE

Chemistry: Ca2(Mn, Fe, Mg)Al2(BO3OH)(SiO3)4, Calcium Manganese Iron Magnesium Aluminum Borosilicate Hydroxide

Class: Silicates

Subclass: Cyclosilicates

Uses: Only as a mineral specimen

Specimens

Axinite is an interesting mineral and produces unique flattened spatula shaped crystals that fanciers of well formed crystals love to collect. It is a triclinic mineral which means that it has

no symmetry planes or axes of rotation. It does possess a center of symmetry. A center of symmetry, or center, is a

symmetry operation that takes a face on one side of a crystal and inverts in through the center of the crystal to the other side. The faces that are inverted are completely flipped both left to right and up to down. With this being the only symmetry operation, faces on axinite crystals are seemingly scattered everywhere and anywhere (except for their inverted partners on the other side of the crystal). Axinite is actually a series name for a group of isostructural minerals. All have the same structure but are different in terms of chemistry. They are named for their respective enrichment in either iron, magnesium and manganese, except for the iron manganese intermediate tinzenite. They differ slightly in color and specific gravity and most collectors refer to any of them as simply axinite, that is why they are treated as a single mineral here. Below is a list of the members of the axinite series and some of their properties:

Ferro-axinite, iron rich, lilac brown to black, SG=3.31

Magnesio-axinite, magnesium rich, pale blue to gray, SG=3.18

Manganaxinite, manganese rich, yellow-orange,

SG=3.32

Tinzenite, iron & manganese intermediate, yellow,

SG=3.37 Manganaxinite is found at Franklin, New Jersey and is special due to a red fluorescence that is not seen in the other axinites and an attractive yellow-orange color. All axinites can have a one-of-a-kind color and crystal habit and a very nice luster that make them popular for collectors that like a different kind of crystal shape. PHYSICAL CHARACTERISTICS:

Color is commonly a lilac brown but also yellow, yellow-orange, gray, pale blue and even black.

Luster is vitreous.

Transparency crystals are transparent to translucent.

Crystal System is triclinic; bar 1

Crystal Habits include flattened wedge shaped

crystals, often with a spatula or knife-like shaped edge. Also as granular and as parallel bladed aggregates.

Cleavage is good in one direction.

Fracture is conchoidal.

Hardness is 6 - 7.5

Specific Gravity is approximately 3.0 - 3.4 (slightly above average for transparent minerals)

Streak is white.

Other Characteristics: crystals are heavily striated on

some faces and manganese rich axinites have been known to be fluorescent red.

Associated Minerals are diopside, andradite, quartz, calcite, epidote, scheelite and prehnite.

Notable Occurrences include Madera Co., California

and Franklin, New Jersey, USA; Baja California, Mexico; Bahia, Brazil; Switzerland; Obira, Japan; Cornwall, England and France.

Best Field Indicators are crystal habit, hardness, color

and striations.

THE MINERAL AZURITE

Chemistry: Cu3(CO3)2(OH)2, Copper Carbonate Hydroxide

Class: Carbonates

Uses: ornamental stone, pigment, minor ore of copper, and jewelry.

Specimens

Azurite is a very popular mineral because of its unparalleled color, a deep blue called "azure", hence its name. Azure is derived from the arabic word for blue. The color is due to the presence of copper (a strong coloring agent), and the way the

copper chemically combines with the carbonate groups (CO3) and hydroxyls (OH). Azurite has been used as a dye for paints and fabrics for eons. Unfortunately, at times its color is too deep and larger crystals can appear black. Small crystals and crusts show the lighter azure color well. Azurite is often associated with its colorful close cousin, malachite Green malachite is closely associated with azurite in many ways. Not only do they frequently occur together (pictured above), they also have very similar formulae. Malachite can also replace azurite, making a pseudomorph, or an exact copy of an azurite crystal (only now instead of being blue, it would be green). Compare their formulas: Azurite's formula: Cu3(CO3)2(OH)2 Malachite's formula: Cu2(CO3)(OH)2 The charges on the copper ions are the same for both minerals at positive two (each hydroxide has a charge of negative one and each carbonate has a charge of negative two). But what causes the color change from azurite to malachite if the charge on the copper remains the same? Consider the formulas if they are rewritten as so: Azurite's formula: Cu(OH)2-2(CuCO3) Malachite's formula: Cu(OH)2-CuCO3

Notice the different amounts of CuCO3 in the two formulas. The azurite seems to have an extra CuCO3, but the transformation could be explained by an addition of an extra Cu(OH)2 to azurite's formula to make two malachites as in the following equation:

Cu(OH)2-2(CuCO3) + Cu(OH)2 ----> 2{Cu(OH)2-CuCO3}

{AZURITE} 2{MALACHITE}

Since the Cu(OH)2 is more oxidized than the CuCO3, the malachite is therefore more oxidized than azurite. This means

that malachite represents a later stage of oxidation and the increased oxidation is what causes the color change. The actual formula for the conversion is a bit more involved and includes the addition of a water molecule to two azurite molecules and the release of a carbon dioxide molecule; leaving behind three malachite molecules. The equation is represented as follows:

2{Cu(OH)2-2(CuCO3)}

+ H2O --------->

3{Cu(OH)2-CuCO3}

+ CO2

2{AZURITE} {WATER} 3{MALACHITE} {CARBON DIOXIDE}

The oxidation is persistent and actually ongoing, although very slow. Azurite paints made centuries ago have undergone the transformation much to the imagined horror of artists whose paintings of beautiful blue skies now have a most unusual green hue! Thankfully for mineralogists and collectors, this transformation is one of the most asthetically pleasing in the mineral kingdom. Although the malachite may soften the sharpness of the azurite crystal, it generally leaves the specimen intact and a whole range of transformations from pure azurite to pure malachite can be obtained. There really is no comparison to any other mineral to mineral transformation in terms of overall beauty. Azurite is used in jewelry and for dyes as mentioned above. It is also an unimportant ore of copper, although its significance has been more impressive in the past. It is still considered a minor ore of copper; mostly because it is found associated with other more valuable copper ores. Fine crystal clusters, nodular specimens, and interesting and beautiful combinations with malachite are important pieces in anyone's mineral collection. The magnificent color of azurite is worth mentioning again as it truly is a one-of-a-kind in the mineral world. Azurite is one of those classic minerals.

PHYSICAL CHARACTERISTICS:

Color is azure, deep blue or pale blue if found in small

crystals or crusts.

Luster is vitreous to dull depending on habit.

Transparency: Transparent if in thin crystals,

otherwise translucent to opaque.

Crystal System is monoclinic; 2/m.

Crystal Habits crystals are irregular blades with wedge

shaped terminations. Also, aggregate crusts and radiating, botryoidal, nodular and earthy masses.

Cleavage is good in one direction and fair in another.

Fracture is conchoidal and brittle.

Hardness is 3.5-4.

Specific Gravity is 3.7+ (heavier than average).

Streak is blue.

Associated Minerals are numerous and include malachite limonite, calcite, cerussite, quartz, chalcopyrite, native copper, cuprite, chrysocolla, aurichalcite, shattuckite, liroconite, connellite and

other oxidized copper minerals.

Notable Occurrences include numerous localities

worldwide, but special localities produce some outstanding specimens especially from Lasal, Utah; Bisbee, Arizona and New Mexico, USA; Mexico;

Tsumeb, Nambia; Shaba, Congo; Toussit, Morocco; Australia and in many locations in Europe.

Best Field Indicators are color, softness, crystal habits and associations.