MINERALS

What is a mineral?•Naturally occurring•Inorganic •Solid •Crystal shape•Definite chemical composition

Natural crystals •Must be found in nature

•Ex. Cu, Au, SiO2 (quartz)

•Crystal structure•Like NaCl crystals

Inorganic•From a non-living Source (no fossils)

Solid with a formula•Almandine, Fe3Al2(SiO4)3

•Not liquid (Hg) or gas (O2)

•Specific Gravity (density)•Color•Streak•Luster•Hardness•Other properties

How do I identify them?

•SG = ratio of mineral density to water (1.0 g/cm3)•is the same no matter the size of the mineral sample•Ex. Graphite 2.2 g/cm3

Specific Gravity

•Some minerals can only be a certain color (sulfur)•Streak - color left when mineral is rubbed on unglazed porcelain•Ex. pyrite is golden but has a dark grey streak

Color & Streak

•how light reflects off the mineral•metallic vs. non-metallic•Silky, glassy, dull, etc.

Luster

•Mohs hardness scale goes from 1 – 10•1 ~ soft (talc)•10 ~ hard (diamond)

Hardness

•Glow under ultraviolet light (fluorite)•Magnetic (magnetite)

Special Properties