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Mineral- inorganic, naturally occurring substances that have a characteristic chemical composition,

distinctive physical properties, and crystalline structure.

Crystalline structure- orderly 3D arrangement of atoms or molecules.

Crystals- materials with crystalline structure

Exceptions: Limonite & Opal (mineraloids)

Amorphous solid- without crystalline structure (such as Opal). Created as result of fast cooling rate; if

the cooling rate is faster than the rate at which molecules can organize into a more thermodynamically

favorable crystalline state, then an amorphous solid will be formed.

7 properties commonly used to identify minerals:

1. Color2. Crystal form3. Luster4. Streak5. Hardness6. Cleavage7. Fracture

Color and Clarity- 1 color= 1 mineral. (Generally- sometimes certain minerals have a variety of colors,

but are the same mineral. Quartz has a wide array of color variations, for example)

Color is used as a complimentary diagnostic. You CANNOT tell the mineral type by color alone!

Clarity helps determine a mineral type:

1. Transparent- clear2. Translucent- foggy3. Opaque- impervious to light such as metals or concrete

Color/clarity should be recorded hand in hand during diagnostics.

Crystal Form/Habit

Crystal Forms= Geometric shapes (external feature of mineral crystals).

Combination of forms = crystal HABIT.

Most crystals group when forming such as that of calcite. So there you see a crystal habit.

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Luster- A description of how light reflects from the surface of an object , such as a mineral.

2 main types: Metallic (M) and Nonmetallic (NM)

Vary in light intensity from bright (highly reflective, shiny polished) to dull (not very reflective,

shiny, or polished)

Luster of Nonmetallic minerals:

1. Vitreous resembling the luster of freshly broken glass or a glossy photograph2. Waxy- resembling the luster of a candle3. Pearly- resembling the luster of a pearl4. Satiny- resembling the luster of satin or silk cloth5. Earthy- lacking reflection, completely dull, like dry soil.6. Greasy- resembling the luster of grease, oily7. Porcelaneous- resembling the luster of porcelain (translucent white ceramic ware)

Streak- Color of substance after ground into fine powder

Hardness- A measure of resistance to scratching

Cleavage- Cleavage is the way a mineral breaks. Many minerals break along flat planes, or

cleavagessome in only one direction (mica), others in two directions (feldspar), and some in three

directions (calcite) or more (fluorite). Some minerals, like quartz, have no cleavage. Cleavage is a

profound property that results from a mineral's molecular structure, and cleavage is present even

when the mineral doesn't form good crystals. Cleavage can also be described as perfect, good or poor.

P. 55

Fracture- Fracture is breakage that is not flat. The two main kinds of fracture are conchoidal (shell-

shaped, as in quartz) and uneven. Metallic minerals may have a hackly (jagged) fracture. A mineral

may have good cleavage in one or two directions but fracture in another direction.

Mohrs Scale of Hardness- P. 53 in lab manual

Tenacity- Resistance to breakage

Reaction to Acid- Differs among minerals. Carbonates fizz when hydrochloric acid is applied to a

freshly exposed surface. Dolomite fizzes only when surface is scratched.

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Definition ofTerms

Striations- straight hairline grooves on the cleavage of some minerals (plagioclase feldspar & K-spar)

Striations on cleavage faces allow you to differentiate the two. Plagioclase has striations, potassium

feldspar does not. But in most cases any white feldspar is identified as plagioclase and any pink feldspar

as orthoclase.

Porphyritic rx - composed of at least two minerals having a conspicuous (large) difference in grain size.

The larger grains are termed phenocrysts and the finer grains either matrix or groundmass

Aphanitic rx - characterized by textures in which the mineral grains are not visible to the eye so they

generally look rather like a blank slate. Of course, this represents an ideal world. Most aphanitic rocks

will have at least a few phenocrysts (larger grains).

Phaneritic textured rx - comprised of large crystals that are clearly visible to the eye with or without a

hand lens or binocular microscope. The entire rock is made up of large crystals, which are generally 1/2

mm to several centimeters in size; no fine matrix material is present.

Foliated rx- is any penetrative planar fabric present in rocks. Foliation is common to rocks affected by

regional metamorphic compression typical of orogenic belts. Rocks exhibiting foliation include the

typical metamorphic rock sequence of slate, phyllite, schist and gneiss. The slatey cleavage typical of

slate is due to the parallel growth of microscopic mica crystals. In gneiss the foliation is more typically

represented by compositional banding due to segregation of mineral phases.