Rocks & MineralsNOTES

MineralA Naturally Occurring Naturally Occurring Inorganic Solid Inorganic Solid with a definite chemical chemical composition composition and crystaline structurecrystaline structure.

Mineral Properties & Identification

Crystal structure & chemical composition of minerals largely determine physical & chemical

properties used to identify

What causes minerals to have different physical properties?

their internal arrangement of atoms

The Main Physical Properties Used to Identify Minerals

Color

A poor indicator!

Minerals can be multiple colors

Many minerals are the same color

The Main Physical Properties Used to Identify Minerals

Streak

the powder form of a mineralmore reliable than color

Streak-Color of finely crushed residue or powder of a mineral

-When you write on chalkboard, you observe streak of chalk

-Streak of mineral usually consistent, making streak color more useful in identifying than mineral color

The Main Physical Properties Used to Identify Minerals

Luster

how light reflects off a mineral

metallic non-metallic

looks like a metal

looks earthy, waxy, greasy or brilliant

Luster- Shine from an unweathered mineral’s surface- Way a mineral looks in reflected

light- 2 groups of luster

Metallicshine like surface of clean stainless steel potExample: Pyrite & galena

Non-Metalliccan be glassy like black hornblende & quartzcan be pearly like muscovite mica

Hardness

The Main Physical Properties Used to Identify Minerals

resistance to being scratched

It is NOT the same as breaking!

For example: You can break glass easily with steel.However, steel will not scratch glass.

Hardness

The Main Physical Properties Used to Identify Minerals

Scratchability of minerals, not how easily it breaks

For example: Diamonds are hardest mineral, but if you

drop an unmounted diamond on a tile floor it will break

MOH’S SCALE OF HARDNESS

Hardness

Mineral Hardness

Mineral

1 (softest)

Talc 6 Orthoclase

2 Gypsum 7 Quartz3 Calcite 8 Topaz4 Florite 9 Corundum5 Apatite 10

(hardest)Diamond

- Quick way to determine relative hardness is to use piece of window glass1. If mineral scratches glass it is hard2. If mineral doesn’t scratch glass it is soft

Density-Each mineral has specific density or

narrow range of densities-Often stated as specific gravity,

which has no units-Specific gravity is density of mineral

compared to density of water-density is a good test to distinguish

gemstones, because it doesn’t harm samples

Cleavage- Tendency of mineral to break along

zones of weakness & form smooth to semi-smooth parallel sides or surfaces

- Cleavage surfaces can often be distinguished from sides without by having a shiner or more brilliant luster

- If minerals lack preferred zones of weakness, then it will demonstrate uneven breaking surface (fracture)

Fracture

The Main Physical Properties Used to Identify Minerals

the mineral breaks randomly

Crystal Structure

-Outward geometric shape of mineral, crystal form, reflect structure

-Orderly arrangement of atoms in mineral

-Any mineral can have many different crystal shapes

Other Mineral Properties- Some chemical properties of

minerals are used for identification- Reaction of a mineral with

acid