Bannisterite

General Information:
 Chemical Formula:
KCa(Mn,Fe++,Zn)21(Si,Al)32O76(OH)16·12(H2O)
 IMA Status:
Approved IMA 1968
Physical Properties:
 Cleavage:
[001] Perfect
 Color:
dark brown or black.
 Density:
2.83
 Diaphaniety:
Translucent
 Hardness:
4 - Fluorite
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