General Information:
Chemical Formula:
[ ]Ca2(Fe++3AlFe+++)Si6Al2O22(OH)
Composition:
(Molecular Weight = 939.00 gm)
Calcium 8.54 % Ca
Aluminum 8.62 % Al
Iron 23.79 % Fe
Silicon 17.95 % Si
Hydrogen 0.21 % H
Oxygen 40.89 % O
Empirical Formula:
Ca2Fe2+3AlFe3+(Si6Al2O22)(OH)2
IMA Status:
Approved IMA 1978 (Dana # Added)
Name Origin:
Named for its composition and for Gustav Tschermak von Sessenegg (1836-1927), Austrian mineralogist.
Physical Properties:
Cleavage:
[110] Perfect
Color:
green, dark green, or black.
Density:
3.41
Diaphaniety:
Translucent to Subopaque
Hardness:
5-6 - Between Apatite and Orthoclase
Luster:
Vitreous (Glassy)
Streak:
greenish gray
More details...