Minerals

The Geologic Alphabet

Definition of a Mineral

• Natural

• Solid

• Inorganic

• Crystalline Structure

• Chemical CompoundSource: E. R. Degginger/Bruce Coleman Inc.

Mineral Formation

Primary1. Crystallize out of a magma2. Crystallize out of water

Secondary3. Chemical Weathering4. Metamorphism

Form Igneous Rocks

Form Metamorphic Rocks

Form Sedimentary Rocks

Physical Properties of Minerals

A. Mineral Shape

Crystal Form

Source: Jeffrey Scovil

Source: Jeffrey Scovil

FractureConchoidal (“shell-like”)

Mineral Cleavage

3 planes;angle 90°

Source: Ed Degginger/Bruce Coleman Inc.

Halite

1

23

Mineral Cleavage1 plane; angle N/A

Source: Breck P. Kent

1

Muscovite

Mineral Cleavage4 planes; not 90°

Fluorite

1

23

4

Physical Properties of Minerals

B. Mineral Appearance

Color

QuartzColor

Quartz Powder

Streak (Powder Color)

Source: Breck P. Kent

Hematite

Luster

MetallicHighly reflected

and “metal colored”

Nonmetallic VariesVitreous Shines like glass

PearlyWhitish iridescence

(like a pearl)

ResinousDull shine(like wax)

Earthy (Dull)Surface doesn’t

reflect light

Metallic Luster

Source: E. R. Degginger/Earth Scenes Silver

Nonmetallic LusterVitreous

Quartz

Nonmetallic Luster

Earthy (Dull)

Source: Breck P. Kent

Realgar

Optical Properties

1. Opaque2. Translucent3. Transparent

Petrologic Microscope

Biotite in white light

PolarizedLight

Olivine

Quartz

Polarized Light - Calcite

Physical Properties of Minerals

C. Mineral Strength/Density

Mohs Hardness

Scale

Specific Gravity(Density)

Physical Properties of Minerals

D. Other Properties

Reaction to HCl

Magnetism

Taste

Smell

Feel

Striations & Banding

Fluorescence - White light

Source: Breck P. Kent

Fluorescence - UV light

Piezoelectricity

Gems

Mineral Families

Native Elements Oxides

Hematite

Sulfides

Pyrite

Sulfates

Gypsum

Diamond

Halides

Halite

Carbonates

Calcite

Silicates:

Silicon-Oxygen Tetrahedron

Important Silicates

Feldspars

Quartz

Micas

Orthoclase

Muscovite

Olivine

Mafic MineralsLow Silica (Mg, Fe)

vs.

Felsic MineralsHigh Silica (Al, K)

Color

Dark Colored(including black & green)

Light Colored(including white, tan, orange)

Density

Heavy weight

Light weight

Mineral Families

Native Elements Contain 1 element

Oxides Bonded with oxygen (O)

* Carbonates Bonded with carbon (C) and oxygen (O)

Sulfides Bonded with sulfur (S)

Sulfates Bonded with sulfur (S) and oxygen (O)

* Silicates Bonded with silicon (Si) and oxygen (O)

* Halides “Salts”

Hydrous MineralsContain Water

Gypsum Clay Minerals

Biotite

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