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Identification Key for the Rock-Forming Minerals

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This table lists the most important features of the basic rock-forming minerals.

MineralUsual ColorCrystals Cleavages HardnessDiagnostic
BiotiteBlackRare1 perfect2–3Cleavage
CalciteWhiteCommon3 good3Acid fizz
DolomiteWhiteCommon3 good4Acid no fizz
FeldsparWhite or pinkCommon2 good6–6.5Hardness
HornblendeBlackCommon2 (60/120°)5–6Cleavage
MuscoviteWhiteRare1 perfect2–3Cleavage
OlivineGreenCommon1 fair6.5–7Color
PyroxeneDarkRare2 (87/93°)5–6.5Cleavage
QuartzWhiteCommonNone7Fracture

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