What is a mineral?

• • • • • Found in nature Inorganic: not made from living things Always in a solid form Has a crystal structure Definite Chemical composition: always has the same elements is the same amount

Formation of Minerals

• Many minerals come from magma • When magma cools mineral crystals are formed.

• Magma that cools fast has small crystals • Magma that cools slow has large crystals • The two most abundant elements in the earths crust are oxygen and silicon.

Minerals

• • Each mineral has its own specific properties that can be used to identify it. Learning these properties will make it easy to identify minerals.

Hardness

• • • One of the best clues to use is hardness.

Hardness is a mineral’s resistance to being scratched.

Mohs hardness scale – invented by Friedrich Mohs in 1812 • Ranks 10 minerals from softest to hardest

Mohs hardness scale

• • •

1 Talc – softest known mineral. It flakes easily when scratched by fingernail.

2 – Gypsum scratch it.

– a fingernail can easily 3 – Calcite – A fingernail cannot scratch it, but a copper penny can.

Mohs continued

• • • •

4 – Fluorite scratch it.

– A steel knife can easily 5 – Apatite – A steel knife can scratch it.

6 – Feldspar – Cannot be scratched by a steel knife, but it can scratch window glass.

7 – Quartz – Can scratch steel and hard glass easily.

Mohs continued

•

8 – Topaz – Can scratch quartz.

•

9 – Corundum – Can scratch topaz.

•

10 – Diamond – Hardest known mineral. Diamond can scratch all other substances.

Color

• • • • Color is easy to identify Color can be used only to identify a few minerals that always have their own characteristic color.

Azurite – always blue Malachite – always green

Streak

• • • • The streak of a mineral is the color of its powder. You rub the mineral against a streak plate to see the powder.

Pyrite – gold in color – black streak Gold – gold in color – golden yellow streak

Luster

• • • • Luster is how the mineral reflects light Minerals with metals in them are often shiny.

Quartz is glassy.

Other terms to describe luster are metallic, waxy, pearly, earthy, and vitreous,

Density

• • Each mineral has a characteristic density • Density = the measure of how much matter is in a given amount of space.

• No matter what size of the sample, the density will always be the same.

To find the density, measure the mass with a balance and then put the sample in water to find the volume. Use the formula D = Mass/Volume (g/cm³) to calculate.

Cleavage

• Cleavage is the tendency of some minerals to break along smooth, flat surfaces.

• How the atoms in the crystal are arranged will determine if the mineral has cleavage.

• Mica breaks easily into distinct sheets.

Fracture

• • • • Most minerals do not split apart evenly.

Fracture is the tendency of some minerals to break unevenly along curved or irregular surfaces . Quartz – shell-like shaped fracture, looks like chipped glass Pure metals – form jagged points

Special properties

• • • • • Fluorite and Calcite are minerals that glow under ultraviolet light Magnetite is a natural magnet that attracts iron. Calcite will bubble or “fizz” when acid is placed on it.

Halite taste salty Minerals that contain radium and uranium are radioactive.

Mining Minerals

An ore is a mineral deposit large enough and pure enough to be mined for profit.

Mining 1. Strip mining – earthmoving equipment scrapes away soil to expose ore 2. Open-pit – miners use giant earthmoving equipment to dig a tremendous pit 3. Shaft mining – network of tunnels that extend deep into the ground.

Reclamation

Mining can be harmful to the environment.

Reclamation – process by which land used for mining is returned to its original state or better.

Another way to reduce the effects of mining is to reduce our need for minerals - recycling

Essential Questions

Please answer in complete sentences • • • • What properties can you use to determine the type of mineral?

Describe how you can test a mineral to determine its hardness, density, and streak.

How are cleavage and fracture similar? How are they different?

Explain why you can’t rely on any single test or property when you are trying to identify a mineral.