Rocks & Minerals

NOTES

What is a mineral?

It is a

substance which has a

naturally occurring inorganic

definite chemical composition

ESRT Mineral Chart Click Here

Naturally Occurring

Formed in nature & not made by people

Inorganic

Has not been made by or composed of life forms

-Fossil Fuels are NOT a minerals because they comes from microogranisms

-A pearl is NOT a mineral because it comes from an oyster

-Definite Chemical Composition

-Solids composed of 1 or more chemical elements

-All minerals are rocks-Not all rocks are minerals

-Rock is any naturally formed solid that is part of Earth or any other celestial body

-Glasses are not minerals because their atoms are not arranged in a specific pattern

- 20-30 common rock forming minerals

Crystal Structure-responsible for many of minerals

chemical & physical properties such as crystal form, breaking pattern & hardness

-Most rock-forming minerals are silicates

-Silicate minerals have structure that results from various arrangements of tetrahedron-shaped unit on oxygen & silicon-Tetrahedron can be arranged in

different ways resulting in different breaking patterns

Minerals have a definite chemical composition.

What two elements, by mass, make up the greatestpercentage of the Earth’s crust?

siliconoxygen

Minerals have a definite chemical composition.

These two elements combine to form compounds called

silicates (SiO4)

Minerals have a definite chemical composition.

They combine in a specific structure called a:

silicon-oxygen tetrahedra

Mineral Formation: by 1 of 2 processes1. Inorganic Crystallization

- Process of organizing atoms to form crystalline solids

2. Recrystallizaiton- From solids, liquids & gases associated with various rock-forming environments

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

Luster- Shine from an unweathered

mineral’s surface

- Way a mineral looks in reflected light

- 2 groups of lusterMetallic

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

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

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

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 Quartz

3 Calcite 8 Topaz

4 Flvorite 9 Corundum

5 Apatit 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 not units

-Specific gravity is density of mineral compared to density of water

-Specific density 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 acidWhen small amount of dilute HCl

placed on mineral or rock containing calcite (CaCO3) will bubble (effervesce) – giving off CO2

Dolomite distinguished from calcite, because dolomite will only bubble in acid after powdered

What two elements, by mass, make up the greatest percentage of the Earth’s crust? Silicon

Potassium

These two elements combine to form compounds called