General Information:
Chemical Formula:
KFe++2(Nb,Ta)(PO4)2O2·2(H2O)
Composition:
(Molecular Weight = 523.68 gm)
Potassium 7.47 % K
Tantalum 8.64 % Ta
Niobium 13.31 % Nb
Iron 21.33 % Fe
Phosphorus 11.83 % P
Hydrogen 0.77 % H
Oxygen 36.66 % O
Empirical Formula:
KFe2+2Nb0.75Ta0.25(PO4)2O2·2(H2O)
IMA Status:
Approved IMA 1976
Physical Properties:
Cleavage:
[100] Good, [001] Good
Color:
brown, reddish brown, or black.
Density:
3.31 - 3.36, Average = 3.33
Diaphaniety:
Transparent to Translucent
Hardness:
4 - Fluorite
Luster:
Subadamantine
Streak:
olive green
More details...