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Formulas of Rock-Forming Minerals

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Fewer than a dozen minerals account for the vast volume of the world's rocks. These rock-forming minerals make up substantial portions, even the totality, of the rocks they occur in. Here they are, with their formulas.

MineralApproximate Chemical Composition
Plagioclase feldsparNaAlSi3O8 to CaAl2Si2O8 (continuous series)
Potassium feldsparKAlSi3O8
QuartzSiO2
Pyroxene(Mg,Fe)2Si2O6 (enstatite series) and
(Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6 (augite)
BiotiteK(Fe,Mg)3AlSi3O10(OH)2
MuscoviteKAl2(Si3Al)O10(OH,F)2
Hornblende(Ca,Na)2–3(Mg,Fe,Al)5[(Si,Al)8O22](OH)2
Olivine(Fe,Mg)2SiO4
CalciteCaCO3
DolomiteCaMg(CO3)2

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