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Classification of mineralsClassification of minerals

According to characteristicsAccording to characteristics E.g. Minerals with metallic luster, Green E.g. Minerals with metallic luster, Green

minerals, minerals with cleavage, etc. minerals, minerals with cleavage, etc.

According to crystal shapeAccording to crystal shape E.g. Cubic minerals. E.g. Cubic minerals.

According to chemistryAccording to chemistry E.g. Minerals containing Si. E.g. Minerals containing Si.

Why classify minerals?

Classifying mineralsClassifying minerals

Dana’s Classification SystemDana’s Classification System

http://www.webmineral.com/http://www.webmineral.com/danaclass.shtmldanaclass.shtml

Based on chemical composition and Based on chemical composition and structurestructure

Classifying mineralsClassifying minerals

Biggest group of minerals: silicatesBiggest group of minerals: silicates Non-silicates:Non-silicates:

Native elementsNative elements HalidesHalides Carbonates, Nitrates, Borates Carbonates, Nitrates, Borates Sufates, Chromates, MolybdenatesSufates, Chromates, Molybdenates Phosphates, Arsenates, VanadatesPhosphates, Arsenates, Vanadates

– ““Ore minerals”:Ore minerals”: SulfidesSulfides Oxides/hydroxidesOxides/hydroxides

TodayToday

SiOSiO22 minerals (i.e. quartz/chalcedony) minerals (i.e. quartz/chalcedony)

Corundum (AlCorundum (Al22OO33)) Carbonates Carbonates

Calcite, Aragonite (CaCOCalcite, Aragonite (CaCO33, Dolomite , Dolomite (CaMg(CO(CaMg(CO33))22), Siderite (FeCO), Siderite (FeCO33))

Halides (salts)Halides (salts) Halite (NaCl), Fluorite (CaFHalite (NaCl), Fluorite (CaF22))

PhosphatesPhosphates Apatite CaApatite Ca55(PO(PO44))33(OH,F,Cl)(OH,F,Cl)

Quartz (SiOQuartz (SiO22)) Color:Color: VariableVariable. . Clear, purple, pink, etc.Clear, purple, pink, etc. Transparency:Transparency: Crystals are transparent to translucent, Crystals are transparent to translucent,

cryptocrystalline forms can be translucent or opaque. cryptocrystalline forms can be translucent or opaque. Crystal SystemCrystal System is trigonal; is trigonal; 3 2.3 2. Crystal Habits:Crystal Habits: Widely variable. Look for Widely variable. Look for characteristic characteristic

crystal shape (hexagonal crystals with a six sided crystal shape (hexagonal crystals with a six sided pyramid termination)pyramid termination). Cryptocrystalline or massive . Cryptocrystalline or massive forms may be botryoidal, globular, stalactitic, etc. forms may be botryoidal, globular, stalactitic, etc.

Cleavage:Cleavage: very weak in three directions rhombohedral). very weak in three directions rhombohedral). Fracture:Fracture: conchoidalconchoidal Hardness: 7Hardness: 7,, less in cryptocrystalline forms. less in cryptocrystalline forms. Specific Gravity: Specific Gravity: 2.652.65 or less if cryptocrystalline. or less if cryptocrystalline. Streak: Streak: white. white.

http://mineral.galleries.com/minerals/silicate/quartz/quartz.htm

Quartz SiO2

Clear Quartz

Amethyst

Smoky Quartz

Rose Quartz

Cryptocrystalline Quartz SiO2

Chert/Agate/Chalcedony

Quartz (SiOQuartz (SiO22))Diagnostic featuresDiagnostic features

Very common. Very common. Transparency:Transparency: Usually more transparent Usually more transparent

than feldspar. than feldspar. To tell apart from calcite (esp. To tell apart from calcite (esp.

cryptocrystalline forms):cryptocrystalline forms): No reaction No reaction with acid. with acid.

Crystal Habits:Crystal Habits: Crystals have Crystals have characteristic shape. characteristic shape.

Fracture:Fracture: conchoidal. conchoidal. Usually no Usually no cleavage. cleavage.

Hardness: 7Hardness: 7,, less in cryptocrystalline less in cryptocrystalline forms. Harder than feldspar, calcite. forms. Harder than feldspar, calcite.

http://mineral.galleries.com/minerals/silicate/quartz/quartz.htm

Corundum (AlCorundum (Al22OO33)) Color:Color: Highly variable.Highly variable. White or colorless, blue, White or colorless, blue,

red, yellow, green, brown, purple, and pink; red, yellow, green, brown, purple, and pink; samples can have color zonation.samples can have color zonation.

Luster:Luster: Vitreous to adamantine.Vitreous to adamantine. Transparency:Transparency: Transparent to translucent.Transparent to translucent. Crystal System:Crystal System: Trigonal; bar 3 2/mTrigonal; bar 3 2/m Crystal Habits:Crystal Habits: Sapphire crystals - Sapphire crystals - six-sided six-sided

barrel shaped.barrel shaped. Ruby - Ruby - hexagonal prisms and hexagonal prisms and blades.blades.

Cleavage:Cleavage: None. None. Fracture:Fracture: Conchoidal.Conchoidal. Hardness:Hardness: 99 Specific Gravity:Specific Gravity: Approximately 4.0+ (above Approximately 4.0+ (above

average for translucent minerals) average for translucent minerals) Streak:Streak: White, harder than streak plate. White, harder than streak plate. http://mineral.galleries.com/minerals/oxides/corundum/corundum.htm

Corundum (AlCorundum (Al22OO33))

http://mineral.galleries.com/minerals/oxides/corundum/corundum.htm

RARERARE Luster:Luster: Vitreous to adamantine.Vitreous to adamantine. Transparency:Transparency: Transparent to translucent.Transparent to translucent. Crystal Habits:Crystal Habits: Sapphire crystals - Sapphire crystals - six-six-

sided barrel shaped.sided barrel shaped. Ruby - Ruby - hexagonal hexagonal prisms and blades.prisms and blades.

Cleavage:Cleavage: None. None. Fracture:Fracture: Conchoidal.Conchoidal. Hardness:Hardness: 9 9 (Harder than quartz)(Harder than quartz) Specific Gravity:Specific Gravity: Approximately 4.0+ Approximately 4.0+

(above average for translucent minerals) (above average for translucent minerals)

http://mineral.galleries.com/minerals/oxides/corundum/corundum.htm

Corundum (AlCorundum (Al22OO33))Diagnostic featuresDiagnostic features

Carbonates Carbonates Calcite, Aragonite (CaCOCalcite, Aragonite (CaCO33, Dolomite , Dolomite

(CaMg(CO(CaMg(CO33))22), Siderite (FeCO), Siderite (FeCO33))

ACIDACID

CaCOCaCO33 + 2HCl + 2HCl CaCl2 + H CaCl2 + H22O+ O+ COCO22

Calcite, Aragonite -> Strong reaction to cold acidCalcite, Aragonite -> Strong reaction to cold acid Dolomite, Siderite -> Weak reaction to acidDolomite, Siderite -> Weak reaction to acid

Calcite (CaCOCalcite (CaCO33)) Color:Color: extremely variable but generally white or colorless or extremely variable but generally white or colorless or

with light shades of yellow, orange, blue, pink, red, brown, with light shades of yellow, orange, blue, pink, red, brown, green, black and gray. green, black and gray.

Luster:Luster: Vitreous to resinous to dull in massive forms. Vitreous to resinous to dull in massive forms. Transparency:Transparency: Crystals are transparent to translucent. Crystals are transparent to translucent. Crystal System:Crystal System: Trigonal; bar 3 2/m Trigonal; bar 3 2/m Crystal Habits:Crystal Habits: See web site for many crystalline forms. Also See web site for many crystalline forms. Also

massive, fibrous, concretionary, stalactitic, nodular, oolitic, massive, fibrous, concretionary, stalactitic, nodular, oolitic, stellate, dendritic, granular, layered, etc. etc. stellate, dendritic, granular, layered, etc. etc.

Cleavage:Cleavage: Perfect in three directions, forming rhombohedrons. Perfect in three directions, forming rhombohedrons. HardnessHardness is 3 (only on the basal pinacoidal faces, calcite has a is 3 (only on the basal pinacoidal faces, calcite has a

hardness of less than 2.5 and can be scratched by a fingernail). hardness of less than 2.5 and can be scratched by a fingernail). Specific GravitySpecific Gravity is approximately 2.7 (average) is approximately 2.7 (average) StreakStreak is white. is white. Reacts vigorously with acid.Reacts vigorously with acid.

http://mineral.galleries.com/minerals/carbonat/calcite/calcite.htm

Calcite (CaCOCalcite (CaCO33))Diagnostic featuresDiagnostic features

Very commonVery common Reacts vigorously with acid.Reacts vigorously with acid. Cleavage:Cleavage: Perfect in three directions, Perfect in three directions,

forming rhombohedrons. forming rhombohedrons. HardnessHardness:: 3 (soft) 3 (soft)


Calcite (CaCOCalcite (CaCO33))


Aragonite (CaCOAragonite (CaCO33)) Color:Color: White or colorless or with usually subdued shades of White or colorless or with usually subdued shades of

red, yellow, orange, brown, green and even blue. red, yellow, orange, brown, green and even blue. Luster:Luster: Vitreous to dull. Vitreous to dull. Transparency:Transparency: Crystals are transparent to translucent. Crystals are transparent to translucent. Crystal System:Crystal System: Orthorhombic; 2/m 2/m 2/m Orthorhombic; 2/m 2/m 2/m Crystal Habits:Crystal Habits: Hexagonal, often thin elongated prismatic, Hexagonal, often thin elongated prismatic,

curved bladed, steep pyramidal (spiked) and chisel shaped curved bladed, steep pyramidal (spiked) and chisel shaped crystals. Can also be compact, granular, radially fibrous and crystals. Can also be compact, granular, radially fibrous and massive. Its massive forms can be layered, coralloid, massive. Its massive forms can be layered, coralloid, pisolitic, oolitic, globular, stalachtitic and encrusting. The pisolitic, oolitic, globular, stalachtitic and encrusting. The shells of many species are made up of aragonite. shells of many species are made up of aragonite.

Cleavage:Cleavage: Distinct in one direction (pinacoidal). Distinct in one direction (pinacoidal). Hardness:Hardness: 3.5 - 4 (harder than calcite) 3.5 - 4 (harder than calcite) Specific Gravity:Specific Gravity: 2.9+ (average for non-metallic minerals) 2.9+ (average for non-metallic minerals) Streak: Streak: is white. is white. Reacts vigorously with acid. Reacts vigorously with acid. Best Field IndicatorsBest Field Indicators are crystal habits, single plane of are crystal habits, single plane of

cleavage and reaction to acid. cleavage and reaction to acid.

http://mineral.galleries.com/minerals/carbonat/aragonit/aragonit.htm

Aragonite (CaCOAragonite (CaCO33))Diagnostic featuresDiagnostic features

Reacts vigorously with acid. Reacts vigorously with acid. Color:Color: White or colorless or with usually subdued White or colorless or with usually subdued

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

Crystal Habits:Crystal Habits: Easily confused with calcite, and Easily confused with calcite, and is often replaced by it in nature. Look for acicular is often replaced by it in nature. Look for acicular or fibrous habits. Also, coral skeletons, shells, or fibrous habits. Also, coral skeletons, shells, tests, etc. are deposited as aragonite (though they tests, etc. are deposited as aragonite (though they may later be altered to calcite). Massive forms may later be altered to calcite). Massive forms may be indistinguishable from calcite. may be indistinguishable from calcite.

Cleavage:Cleavage: Distinct in one direction (pinacoidal). Distinct in one direction (pinacoidal). Calcite cleaves in three directions. Calcite cleaves in three directions.

Hardness:Hardness: 3.5 - 4 (harder than calcite) 3.5 - 4 (harder than calcite)


Aragonite (CaCOAragonite (CaCO33))


Dolomite (CaMg(CODolomite (CaMg(CO33) ) 22))

Color:Color: Pink or pinkish and can be colorless, white, yellow, Pink or pinkish and can be colorless, white, yellow, gray or even brown or black when iron is present in the gray or even brown or black when iron is present in the crystal. crystal.

Luster:Luster: pearly to vitreous to dull.pearly to vitreous to dull. Transparency:Transparency: crystals are transparent to translucent.crystals are transparent to translucent. Crystal System:Crystal System: trigonal; bar 3 trigonal; bar 3 Crystal Habits:Crystal Habits: saddle shaped rhombohedral twins and saddle shaped rhombohedral twins and

simple rhombs some with slightly curved faces, also simple rhombs some with slightly curved faces, also prismatic, massive, granular and rock forming. Never found prismatic, massive, granular and rock forming. Never found in scalenohedrons.in scalenohedrons.

Cleavage:Cleavage: perfect in three directions forming perfect in three directions forming rhombohedrons.rhombohedrons.

Fracture:Fracture: conchoidal.conchoidal. Hardness:Hardness: 3.5-43.5-4 Specific Gravity:Specific Gravity: 2.862.86 Streak:Streak: white. white. Reacts weakly with acid. Reacts weakly with acid.

http://mineral.galleries.com/minerals/carbonat/dolomite/dolomite.htm

Dolomite (CaMg(CODolomite (CaMg(CO33) ) 22)) Diagnostic featuresDiagnostic features

Reacts Reacts weaklyweakly with acid. with acid. Use this test to Use this test to differentiate it from Calcite and Aragonite. differentiate it from Calcite and Aragonite.

Color:Color: often pink or pinkish and can be colorless, often pink or pinkish and can be colorless, white, yellow, gray or even brown or black when iron white, yellow, gray or even brown or black when iron is present in the crystal. is present in the crystal.

Luster:Luster: pearly to vitreous to dull.pearly to vitreous to dull. Crystal Habits:Crystal Habits: Most commonly massive, looks very Most commonly massive, looks very

much like calcite. much like calcite. Cleavage:Cleavage: perfect in three directions forming perfect in three directions forming

rhombohedrons (just like calcite).rhombohedrons (just like calcite). Fracture:Fracture: conchoidal.conchoidal. Hardness:Hardness: 3.5-43.5-4 (harder than calcite)(harder than calcite)


Dolomite (CaMg(CODolomite (CaMg(CO33) ) 22))


Siderite (FeCOSiderite (FeCO33))

Color:Color: Yellowish brown, brown, gray, yellowish gray, or Yellowish brown, brown, gray, yellowish gray, or greenish gray. greenish gray.

Luster:Luster: Vitreous to pearly Vitreous to pearly Transparency:Transparency: Translucent to subtranslucent Translucent to subtranslucent Crystal System:Crystal System: Trigonal; bar 3 2/m Trigonal; bar 3 2/m Crystal Habits:Crystal Habits: Tabular, massive, botryoidal are found. Tabular, massive, botryoidal are found. Cleavage:Cleavage: perfect in three directions forming perfect in three directions forming

rhombohedrons.rhombohedrons. Fracture:Fracture: Conchoidal. Very brittle fracture producing small, Conchoidal. Very brittle fracture producing small,

conchoidal fragments conchoidal fragments Hardness:Hardness: 3.53.5 Specific Gravity:Specific Gravity: 3.96 (denser than calcite and dolomite)3.96 (denser than calcite and dolomite) Streak:Streak: white. white. Reacts weakly with acid. Reacts weakly with acid.

http://mineral.galleries.com/minerals/carbonat/siderite/siderite.htm

Siderite (FeCOSiderite (FeCO33)) Diagnostic featuresDiagnostic features

Reacts Reacts weaklyweakly with acid with acid (like dolomite) (like dolomite) Specific Gravity:Specific Gravity: 3.96 (use this to 3.96 (use this to

distinguish siderite from dolomite)distinguish siderite from dolomite) Color:Color: Variable – Yellowish, brown, grey.Variable – Yellowish, brown, grey. Crystal Habits:Crystal Habits: Most commonly massive, Most commonly massive,

looks very much like calcite. looks very much like calcite. Cleavage:Cleavage: perfect in three directions perfect in three directions

forming rhombohedrons (like calcite).forming rhombohedrons (like calcite). Fracture:Fracture: conchoidal.conchoidal. Hardness:Hardness: 3.53.5 (harder than calcite)(harder than calcite)


Siderite (FeCOSiderite (FeCO33))


Halite (NaCl)Halite (NaCl) Color:Color: Clear or white but sometimes blue, purple, Clear or white but sometimes blue, purple,

pink, yellow and gray. pink, yellow and gray. Luster:Luster: Vitreous. Vitreous. Transparency:Transparency: Transparent to translucent. Transparent to translucent. Crystal System:Crystal System: Isometric; 4/m bar 3 2/m Isometric; 4/m bar 3 2/m Crystal Habits:Crystal Habits: Predominantly cubes and in Predominantly cubes and in

massive sedimentary beds, but granular, fibrous massive sedimentary beds, but granular, fibrous and compact forms exist. Some crystals show a and compact forms exist. Some crystals show a crystal type called a crystal type called a hopper crystalhopper crystal. .

Cleavage:Cleavage: Perfect in three directions forming Perfect in three directions forming cubes.cubes.

FractureFracture is conchoidal. is conchoidal. Hardness:Hardness: 2 (softer than calcite) 2 (softer than calcite) Specific Gravity:Specific Gravity: 2.1+ (light) 2.1+ (light) Streak:Streak:White.White. Taste:Taste: Salty Saltyhttp://mineral.galleries.com/minerals/halides/halite/halite.htm

Halite (NaCl)Halite (NaCl)Diagnostic featuresDiagnostic features

Taste:Taste: SaltySalty Transparency:Transparency: Transparent to translucent. Transparent to translucent. Crystal Habits:Crystal Habits: Look for cubic crystals or Look for cubic crystals or

fragments fragments Cleavage:Cleavage: Perfect in three directions Perfect in three directions

forming forming cubes.cubes. FractureFracture is conchoidal. is conchoidal. Hardness:Hardness: 2 (softer than calcite) 2 (softer than calcite) Specific Gravity:Specific Gravity: 2.1+ (light) 2.1+ (light) Streak:Streak:White.White.

http://mineral.galleries.com/minerals/halides/halite/halite.htm

Halite (NaCl)Halite (NaCl)


Fluorite CaFFluorite CaF22

Color:Color: Extremely variable. Can be an intense purple, blue, Extremely variable. Can be an intense purple, blue, green or yellow; also colorless, reddish orange, pink, white and green or yellow; also colorless, reddish orange, pink, white and brown. A single crystal can be multi-colored. But most often brown. A single crystal can be multi-colored. But most often purple. purple.

Luster:Luster: Vitreous. Vitreous. Transparency:Transparency: Transparent to translucent.Transparent to translucent. Crystal System:Crystal System: Isometric; 4/m bar 3 2/mIsometric; 4/m bar 3 2/m Crystal Habits:Crystal Habits: Very often found as crystals with free faces, Very often found as crystals with free faces,

in veins and geodes. Crystals are typically cubes, to a lesser in veins and geodes. Crystals are typically cubes, to a lesser extent, octahedra. Also other rarer isometric habits. Always extent, octahedra. Also other rarer isometric habits. Always with equant crystals; less common are crusts and botryoidal with equant crystals; less common are crusts and botryoidal forms. forms. TwinningTwinning also produces penetration twins that look like also produces penetration twins that look like two cubes grown together.two cubes grown together.

Cleavage:Cleavage: Perfect in 4 directions forming octahedrons. Perfect in 4 directions forming octahedrons. Fracture:Fracture: Irregular and brittle.Irregular and brittle. Hardness:Hardness: 44 (Softer than quartz)(Softer than quartz) Specific Gravity:Specific Gravity: 3.1+ (average) 3.1+ (average) Streak:Streak: is white. is white.

http://mineral.galleries.com/minerals/halides/fluorite/fluorite.htm

Fluorite (CaFFluorite (CaF22)) Diagnostic featuresDiagnostic features

Color:Color: Most often purple, but this is not a reliable Most often purple, but this is not a reliable diagnostic feature as color can vary widely. diagnostic feature as color can vary widely.

Transparency:Transparency: Transparent to translucent.Transparent to translucent. Crystal System:Crystal System: Isometric; 4/m bar 3 2/mIsometric; 4/m bar 3 2/m Crystal Habits:Crystal Habits: Look for cubic and octahedral Look for cubic and octahedral

crystals, but also found in other forms such as crystals, but also found in other forms such as crusts and botryoidal masses. crusts and botryoidal masses.

Cleavage:Cleavage: Perfect in 4 directions forming Perfect in 4 directions forming octahedrons. octahedrons.

Hardness:Hardness: 44 (Softer than quartz)(Softer than quartz) Differentiate from quartz – hardnessDifferentiate from quartz – hardness Differentiate from calcite – no acid reactionDifferentiate from calcite – no acid reaction


Fluorite (CaFFluorite (CaF22))

http://mineral.galleries.com/minerals/halides/fluorite/fluorite.htm

Apatite (CaApatite (Ca55(PO(PO44))33(OH,F,Cl))(OH,F,Cl)) Color:Color: Typically green but also yellow, blue, reddish brown and purple. Typically green but also yellow, blue, reddish brown and purple. Luster:Luster: Vitreous to greasy and gumdrop. Vitreous to greasy and gumdrop. Transparency:Transparency: Transparent to translucent. Transparent to translucent. Crystal System:Crystal System: Hexagonal; 6/m Hexagonal; 6/m Crystal Habits:Crystal Habits: Typically a hexagonal prism with the hexagonal Typically a hexagonal prism with the hexagonal

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

Cleavage:Cleavage: Indistinct in one basal direction. Indistinct in one basal direction. Fracture:Fracture: Conchoidal. Conchoidal. Hardness:Hardness: 5 (softer than quartz). 5 (softer than quartz). Specific Gravity:Specific Gravity: Approximately 3.1 - 3.2 (average for translucent Approximately 3.1 - 3.2 (average for translucent

minerals) minerals) Streak:Streak: White. White. Other Characteristics:Other Characteristics: An unusual "partially dissolved" look similar to An unusual "partially dissolved" look similar to

the look of previously sucked on hard candy. the look of previously sucked on hard candy.

http://mineral.galleries.com/minerals/phosphat/apatite/apatite.htm

Apatite (CaApatite (Ca55(PO(PO44))33(OH,F,Cl))(OH,F,Cl))Diagnostic featuresDiagnostic features

Color:Color: Typically green but also yellow, blue, reddish Typically green but also yellow, blue, reddish brown and purple. brown and purple.

Luster:Luster: Vitreous to greasy and gumdrop. Vitreous to greasy and gumdrop. Transparency:Transparency: Transparent to translucent. Transparent to translucent. Crystal Habits:Crystal Habits: Usually long, hexagonal prismatic Usually long, hexagonal prismatic

crystals. crystals. Cleavage:Cleavage: Indistinct in one basal direction. Indistinct in one basal direction. Fracture:Fracture: Conchoidal. Conchoidal. Hardness:Hardness: 5 (softer than quartz). 5 (softer than quartz). Other Characteristics:Other Characteristics: An unusual "partially An unusual "partially

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

Differentiate from Corundum - hardnessDifferentiate from Corundum - hardnesshttp://mineral.galleries.com/minerals/phosphat/apatite/apatite.htm

http://mineral.galleries.com/minerals/phosphat/apatite/apatite.htm

Apatite (CaApatite (Ca55(PO(PO44))33(OH,F,Cl))(OH,F,Cl))

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