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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