Chlorite group
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The chlorites are the group of phyllosilicate minerals common in low-grade metamorphic rocks and in altered igneous rocks. Greenschist, formed by metamorphism of basalt or other low-silica volcanic rock, typically contains significant amounts of... Wikipedia
Cleavage: Perfect 001
Color: Various shades of green; rarely yellow, red, or white
Crystal habit: Foliated masses, scaley aggregates, disseminated flakes
Crystal system: Monoclinic 2/m; with some triclinic polymorphs
Formula (repeating unit): (Mg,Fe)3(Si,Al)4O10(OH)2·(Mg,Fe)3(OH)6
Fracture: Lamellar
IMA symbol: Chl