What is a Mineral? • Minerals are naturally occurring, inorganicsolid with a chemical composition and a definite crystalline structure • Formed by natural processes • Not alive; never were alive • Has a definite shape and definite volume • Specific chemical composition • Atoms are arranged in repeating patterns
Where do Minerals Come From? • Magma • Compounds in magma react chemically with each other when it cools down • Solution • Minerals can come out of (“precipitate”) from solution
Groups of Minerals • Silicates • Contain silicon, oxygen • 96% of all minerals • Ex: Feldspar, Quartz, Mica • Carbonates • 1 or more metallic elements with CO3 (carbonate) • Found in limestone, marble • Oxides • Oxygen and a metal • Hematite, Magnetite
Other Groups • Sulfides (sulfur and one other element) • Sulfates (contain sulfate, SO4) • Halides (contain chloride, fluoride with a metal…are salts) • Ex: NaCl (sodium chloride, AKA Table Salt) • Native Elements • Silver, Copper • Contain only one element
How to ID a Mineral • Color • Most noticeable • Least reliable • Luster • Way it reflects light from its surface • “Shiny-ness” • Metallic or Non-metallic • Texture • Rough? Greasy? Glassy? Smooth? Etc. • Streak • Color of a mineral when it’s broken/powdered • Can be different from the mineral’s color • Can only be used on minerals softer than porcelain
How to ID a Mineral • Hardness • Very useful • Use Mohs scale • Talc is softest/Diamond is hardest • Which mineral scratches which? • Any mineral with a greater hardness than another mineral will scratch that softer mineral.
How to ID a Mineral • Cleavage • When a mineral splits easily along a flat plane • Clean break • Fracture • When a mineral breaks with rough or jagged edges • Density • Mass per unit of volume • D = m/v • Doesn’t depend on size/shape • Useful • Measured by specific gravity • Ratio of the weight of a substance to the weight of the same amount of water at 4°C
How to ID a Mineral • Special Properties • Effervescence (fizzing) • Calcite • Magnetism • Magnetite • Odor • Sulfur (matchstick, rotten eggs) • Taste • Halite (salty)
Uses For Minerals • Ores • Contains a useful substance that can be mined as a profit • Hematite mined for iron • Rutile contains titanium (for lightweight equipment) • When mineral isn’t profitable (another substance is found to work better, something else is cheaper, etc) it is no longer considered an ore.
Uses For Minerals • Gems • Valuable minerals prized for their rarity, beauty • Polished, used for jewelry