Minerals

What is a mineral?

Any substance that:

1) Is naturally occuring.

2) Is solid

3) Is organic

4) Has a definite chemical composition.

5) Has a crystal system

Naturally Occuring

• Anything that is found/created in nature.

• Most minerals are formed:– From cooled water

solutions.– From Cooled magma– From evaporation of

solutions.

Inorganic: Any material that did not form from living material.

- Some rocks are organic (coal, limestone).

Definite Chemical Composition

A mineral will always have certain elements in distinct proportions.

- Some are pure

elements:

EX: Gold = Au

Silver = Ag

- Some are compounds:

EX: Pyrite = FeS2

Quartz = SiO2

Crystal Systems

Crystal Structure: The Repeating Pattern of a mineral’s particles.

- Shape of the crystal depends on its definite chemical composition.

- Size depends on how quickly the mineral cooled.- The faster = smaller- The smaller = larger

Mineral properties

There are 8 characteristics that are unique between different minerals.

– Hardness– Luster– Streak– Breakage– Crystal shape– Color– Special Properties– Density (Specific Gravity)

hardnessThe measure of how

easily a mineral can be scratched.

Moh’s Hardness Scale- Tested by performing

a scratch test.- On a scale 1-10

1 = softest (Talc)

10 = hardest (diamond)

Luster

How a mineral reflects light.

- EX: Metallic

Glassy/Vitreous

Streak

Color left behind by a mineral.

Tested by:

Scraping a mineral against a piece of unglazed tile and observing the color left behind.

breakageHow a mineral

breaks apart.

2 ways a mineral can break:

1) Cleavage: Breaks with clean smooth edges.

2) Fracture: Breaks with rough uneven edges.

Crystal systems

The shape of a mineral’s crystal.

• Determined by the chemical composition.

• Common:– Hexagonal– Cubic– Triclinic– Monoclinic

Color and Density

Color: The color of the mineral itself.

- Cannot be used alone to identify a mineral because many minerals can come in many different colors.

Density (specific gravity): How much a mineral weighs depending on how big it is.

D = m/v (mass/volume)

Special properties

Some minerals exhibit unique characteristics

- Magnetism- Radioactivity- Fluorescence- Etc…

How are these used?

We use these 8 properties to identify an unknown mineral.

- Tests are performed and compared to known minerals and their properties.