Unit 5:. Minerals are: Solid Formed in nature Inorganic Of a definite composition Composed of...
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Transcript of Unit 5:. Minerals are: Solid Formed in nature Inorganic Of a definite composition Composed of...
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