General Information:
Chemical Formula:
(K,Na,Ca)3(Mn,Fe++)7(Zr,Nb)2Si8O27(OH,F)4
IMA Status:
Approved IMA 1972
Physical Properties:
Cleavage:
[001] Perfect
Color:
dark brown, black, or black brown.
Density:
3.34
Diaphaniety:
Translucent to Opaque
Hardness:
4-4.5 - Between Fluorite and Apatite
Luster:
Vitreous - Adamantine
Streak:
light brown
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