Zircophyllite

Zircophyllite is a complex mineral, formula (K,Na)3(Mn,Fe)7(Zr,Ti,Nb)2Si8O24(OH,F)7. It crystallizes in the triclinic - pinacoidal crystal class as dark brown to black micaceous plates. It has perfect 001 cleavage, a Mohs hardness of 4 to 4.5 and a specific gravity of 3.34. Its indices of refraction are nα=1.708 nβ=1.738 nγ=1.747 and it has a 2V optical angle of 62°.
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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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