Unit 5:

Minerals are: Solid Formed in nature Inorganic Of a definite

composition Composed of a

particular crystal structure

Minerals are formed by natural processes

Minerals are Inorganic Inorganic – not formed from living

matter Minerals are not living and never were

living Salt is a mineral, coal and sugar are not

All minerals are solid – definite shape, definite volume

Most are compounds, some are elements

Contain same elements in same ratio Ex: SiO2

Crystals are solids with repeating patterns

More space = better crystal formation

Minerals can form from Magma Magma – molten material found beneath

Earth’s surface If magma cools slowly in Earth’s

heated interior, large crystals can form

If magma cools at Earth’s surface, or comes into contact with air or water, smaller crystals form

Minerals can also form from a solution

Supersaturated solutions will cause crystals to precipitate

If the liquid of a solution evaporates, the remaining elements form crystals

Silicates – Silicon + Oxygen + Metal(s) Ex: Olivine - Mg2SiO4

Carbonates – CO3 and Metal(s) Ex: Calcite - CaCO3

Oxides – Oxygen and Metal(s) Ex: Hematite– Fe2O3

Sulfates – SO4 and Metal(s) Anhydrite CaSO4

Sulfides – Sulfur and Metal(s) Pyrite – FeS2

Halides – Halogen (Cl or F) and Metal(s) Halite - NaCl

Minerals can be identified through several simple tests

Color can be caused by trace compounds in a mineral

Color is one of the least reliable tests: Why?

The way a mineral reflects light from its surface is called luster

Luster can be classified as either metallic or nonmetallic

Texture describes how a mineral feels to the touch

Can be described as smooth, rough, ragged, greasy, soapy, or glassy

Minerals rubbed on an unglazed porcelain plate may leave a colored, powdered streak on the plate

Streak is the color of a mineral when it is broken up and powdered

Streak may not match a mineral’s external color

Streak rarely changes, even after weathering

Minerals must be softer than a porcelain plate

Hardness measures how easily a mineral can be scratched

Measured on the Mohs Hardness Scale

A mineral will scratch all elements with a softer hardness on the scale

A mineral that breaks along one or more flat planes is said to have cleavage

Minerals that break with rough or jagged edges are said to have fracture

The ratio of the weight of a substance to that of water is specific gravity

Density does nor depend on the amount of the substance, so it is very useful for identification

Ores contain useful substances that can be mined for a profit Ex: Bauxite – aluminum

Gems are prized for their rarity and beauty Ex: Rubies