Minerals and Rocks

Rocks Aggregates (mixture—can be separated) of minerals.

Minerals Four Characteristics: –Naturally occurring –Inorganic (was never alive) –Solid –Possesses a definite chemical structure

Properties of Minerals Crystal form— external expression of internal structure

Properties of Minerals Color—unreliable in identifying minerals

Properties of Minerals Streak—the color of a mineral in its powder form—obtained by rubbing the mineral across a hard, unglazed porcelain

Properties of Minerals Hardness—resistance of a mineral to abrasion or scratching –Mohs scale—hardness scale ranging from 10 (hardest) to 1 (softest) –Diamond is 10, talc is 1

Properties of Minerals Cleavage—tendency of a mineral to break along planes of weak bonding

Properties of Minerals Fracture—do not exhibit cleavage when broken Specific gravity—the weight of a mineral compared to the same volume of water

Mineral Groups Silicates –Silicon and oxygen are the two most abundant elements in the Earth’s crust; they form silicates –All have the same basic structure—the silicon-oxygen tetrahedron—four oxygen atoms surrounding a silicon atom –Other elements join the tetrahedrons together in chains, sheets, or three- dimensional networks. –Feldspars are most abundant, with quartz second

Mineral Groups Carbonates –Calcite Limestone—used in building and paving Marble—used decoratively Halite (salt) and Gypsum also found in sedimentary rock

Mineral Resources Reserves—already identified deposits from which minerals can be extracted profitably Ores—useful metallic minerals that can be mined at a profit Changing economic factors determine whether a deposit is profitable to extract