Siderophyllite

minerals

polylithionite

microcline

astrophyllite

Formula: KFe2+2Al(Si2Al2)O10(OH)2
Phyllosilicate (sheet silicate), biotite group, forms a series with polylithionite
Specific gravity: 3
Hardness: 2½
Streak: Greenish grey
Colour: Dark green, brown, black
Solubility:
Common impurities: Ti,Mn,Mg,Ca,Li,Na,Rb,Cs,Cl,H2O
Environments:

Plutonic igneous environments
Pegmatites

Siderophyllite occurs in pegmatites in nepheline syenite, in greisen, in granite and in aplite (HOM).

Localities

At the type locality, Pikes Peak, El Paso county, Colorado, USA, siderophyllite is associated with microcline and astrophyllite (HOM).

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