Pargasite

inosilicate

metamorphic

Formula: NaCa2(Mg4Al)(Si6Al2)O22(OH)2 inosilicate (chain silicate) amphibole
Specific gravity: 3.069 to 3.181
Hardness: 5 to 6
Streak: White
Colour: Green, brown
Environments:

Metamorphic environments

Pargasite is a common component of skarn metamorphosed from siliceous limestone. It also may occur in schist and amphibolite.

Alteration

magnesium-rich tremolite, tschermakite and albite to pargasite and quartz
☐Ca2Mg5Si8O22(OH)2 + ☐Ca2(Mg3Al2)(Si6Al2)O22(OH)2 + 2Na(AlSi3O8) ⇌ 2NaCa2(Mg4Al)(Si6Al2)O22(OH)2 + 8SiO2
(AM 92.4.491)

Common impurities: Ti,Cr,Mn,K,F,H2O,P

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