Minerals

•Minerals have four characteristics

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Naturally occurring—formed by processes on or inside Earth with no input from humans

Living

Inorganic—not made by life processes

Element or compound with a

definite chemical composition

Orderly arrangement of atoms; all minerals are crystalline solids

Crystal—solid with atoms arranged in orderly, repeating patterns

Some crystals form from Some crystals form from magmamagma, , hot melted rock below the Earth’s hot melted rock below the Earth’s surface.surface.

When magma cools slowly, crystals are large.

When magma cools quickly, crystals are small.

Crystals can form from solutions as water evaporates or if too much of a substance is dissolved in water.

• Mineral groups are defined by their composition.

• Silicates contain silicon, oxygen, and one or more other elements; they include most common rock-forming minerals.

• Silicon and oxygen are the two most abundant elements in Earth’s crust; they form the building blocks of many minerals.

DISCUSSION QUESTION:

• What processes can cause crystals to form?

DISCUSSION QUESTION:

• What processes can cause crystals to form?

Crystals form from cooling magma, from evaporating solutions, and from solutions in which too much of a substance is dissolved.

Mineral Identification

• Color and appearance are not enough to distinguish most minerals.

• Hardness is a measure of how easily a mineral can be scratched; the Moh’s scale compares mineral hardness.

1. Talc - easily scratched by the fingernail 2. Gypsum - just scratched by the fingernail 3. Calcite - scratches and is scratched by a copper

coin 4. Fluorite - not scratched by a copper coin and does

not scratch glass 5. Apatite - just scratches glass and is easily

scratched by a knife 6. Orthoclase - easily scratches glass and is just

scratched by a file 7. Quartz - (amethyst, citrine, tiger's-eye, aventurine)

not scratched by a file 8. Topaz - scratched only by corundum and diamond 9. Corundum - (sapphires and rubies) scratched only

by a diamond 10.Diamond - scratched only by another diamond

1 - Talc

2 - Gypsum

3 - Calcite

4 - Flourite

5 - Apatite

6 - Orthoclase

7 - Quartz

8 - Topaz

9 - Corundum

10 - Diamond

• The way a mineral reflects light is its luster.• Luster can be metallic or nonmetallic

• Nonmetallic lusters include dull, pearly, silky, and glassy.

Specific gravity is the relationship between a mineral’s density to the density of water. If the specific gravity is larger than one it will sink in water, if it is smaller than one it will float in water.

Streak is the color of a mineral in powdered form, but the streak test is useful only for minerals softer than the streak plate.

The way a mineral breaks can be a distinguishing characteristic.

Minerals with cleavage break along smooth, flat surfaces.

Minerals with fracture break with uneven, rough, or jagged surfaces.

Some minerals have unique properties that involve light or magnetism.

DISCUSSION QUESTION:

• What are five properties that could be examined to identify a mineral?

DISCUSSION QUESTION:

• What are five properties that could be examined to identify a mineral?

hardness, luster, specific gravity, streak, cleavage, and fracture

Gems—rare and beautiful minerals that are highly prized

The Cullinan diamond

and the Hope diamond

are famous historical gems.

Gems have industrial

applications in abrasives,

lasers, and electronics.

Minerals can contain other useful elements.

An ore is a mineral or rock containing a substance that can be mined at a profit.

Elements must be refined, or purified, from ores.

• Some elements dissolve in fluids, travel through weaknesses in rocks, and in those weaknesses form mineral deposits called vein mineral deposits.

Titanium is a useful element derived from the minerals ilmenite and rutile.

Mica is an example of a mineral with the characteristic of cleavage, because it can be separated into sheets.

Graphite is one of the softest minerals and is used in pencils.

Sulfur is a bright yellow mineral with the distinctive odor of spoiled eggs.

Calcite is a hard carbonate mineral

Feldspar is the most abundant mineral in the Earth's crust

Hematite is an iron based mineral, colored black, silver-gray, reddish brown, or red.

Halite – the mineral sodium chloride also known as table salt