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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