General Information:
Chemical Formula:
K(Fe++,Mg,Fe+++,Al)8(Si,Al)12(O,OH)27·2(H2O)
Environment:
Commonly associated with iron ores.
Locality:
Moravia of Czechoslovakia at Sternberg in a bead of limonite.
Physical Properties:
Cleavage:
[001] Perfect
Color:
brown red, green, golden brown, or black.
Density:
2.77 - 2.96, Average = 2.86
Diaphaniety:
Subtranslucent to opaque
Habits:
Fibrous - Crystals made up of fibers., Foliated - Two dimensional platy forms., Platy - Sheet forms (e.g. micas).
Hardness:
3 - Calcite
Luminescence:
Non-fluorescent.
Luster:
Vitreous - Dull
Streak:
gray white
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