MineralsMinerals

Chapter 4Chapter 4

What is a mineralWhat is a mineral

• Mineral- a naturally occurring, inorganic solid with a specific chemical composition and a definite crystalline structure.

Cubic

Tetragonal

Hexagonal

Orthorhombic

Monoclinic

Triclinic

4.1

What is a mineralWhat is a mineral

• Some minerals form from magma.– Magma- molten material found beneath

Earth’s surface.– The type and amount of elements found in the

magma determine the type of minerals formed– Slow cooling forms large well defined crystals– Fast cooling forms small crystals

4.1

What is a mineralWhat is a mineral

• Some minerals form from a solution– If a solution becomes supersaturated, or

overfilled with solute, mineral crystals may begin to precipitate, or drop out of solution

– When liquid evaporates the solute is left behind and will crystalize

4.1

What is a mineralWhat is a mineral• Mineral groups-

– 3000 minerals are found in the earth’s crust– 30 of these minerals are common– Most common minerals referred to as rock

forming minerals– Most minerals are made of 8 common

minerals

4.1

What is a mineralWhat is a mineral

• Silicates- contain silicon and oxygen and usually one or more other elements– 96% of the minerals on earth are silicates– Feldspar and quartz

4.1

What is a mineralWhat is a mineral

• Carbonates- contain one or more metallic elements with a carbonate compound (CO3)

– Calcite and dolomite– Primary mineral in limestone, coquina, marble

4.1

What is a mineralWhat is a mineral

• Oxide- contain oxygen and a metal– Hematite, magnetite, and uraninite

• Sulfides- composed of one or more elements with sulfur– pyrite

• Sulfates- composed of one or more elements with a sulfate (SO4)

– anhydrite

4.1

What is a mineralWhat is a mineral

• Halides- made up of sodium or fluoride combined with calcium, sodium, or potassium.– Halite (NaCl)

• Native Element- made up of only one type of element– Silver, copper, gold

4.1

Identifying MineralsIdentifying Minerals

• Color- – Most notable– Typically caused by trace elements in the

compound.– Least reliable clue to mineral identification

4.2Calcite

Identifying MineralsIdentifying Minerals

• Luster- the way a mineral reflects light– Metallic luster- reflect light like a metal– Nonmetallic- do not shine like metals

• Dull, pearly, waxy

4.2 Copper

Identifying MineralsIdentifying Minerals

• Texture- describes how a mineral feels to the touch– Smooth– Rough– Ragged– Greasy– Soapy– Glassy

4.2

Identifying MineralsIdentifying Minerals

• Streak- the color of a mineral when it is broken into a powder– Use a unglazed porcelain plate– Can only be used with minerals that are softer

than the porcelain plate– Varying external color and weathering will not

change the streak for a specific mineral.– One of the most reliable test to ID minerals

4.2

Identifying MineralsIdentifying Minerals

Hematite and Galena

Identifying MineralsIdentifying Minerals

• Hardness- a measure of how easily a mineral can be scratched– One of the most reliable test to ID minerals

4.2

Identifying MineralsIdentifying Minerals

• Cleavage and fracture– Cleavage- mineral will split along one or more

flat planes– Fracture- mineral will break with rough or

jagged edges• Conchoidal fracture- break in arc-like patterns

resembling a clam shell

4.2

Mica Obsidian

Identifying MineralsIdentifying Minerals

• Density and specific gravity– Density- mass per unit of volume

• D = m/v

– Specific Gravity- ratio of the weight to the weight of an equal volume of water at 4oC

4.2

Identifying MineralsIdentifying Minerals

• Special Properties– Double refraction- the bending of

light as it passes through a mineral– Effervescent- hemically reacts in

the presence of an acid– Magnetic– Odor- certain sulfur containing

minerals will smell like rotten eggs.– Fluorescence- Glow when exposed

to UV light4.2

Mineral UsesMineral Uses

• Ores- contain a useful mineral that can be mined for profit.– Mines- used to obtain ores

from deep inside the earth’s crust

• Open-pit- clear land and dig a hole to the mineral

– quarry

• Shaft mining- dig a tunnel to remove the ore

4.2

Copper Mine

Mineral UsesMineral Uses

• Gems- valuable minerals that are prized for their rarity and beauty.– Rubies, emeralds, diamonds– Certain impurities (trace elements) might

make one form of a mineral more valuable than another.

• Amethyst- purple version of quartz.

4.2