General Information:
Chemical Formula:
[ ]Ca2(Mg3AlFe+++)Si6Al2O22(OH)2
Composition:
(Molecular Weight = 844.38 gm)
Calcium 9.49 % Ca
Magnesium 8.64 % Mg
Aluminum 9.59 % Al
Iron 6.61 % Fe
Silicon 19.96 % Si
Hydrogen 0.24 % H
Oxygen 45.48 % O
Empirical Formula:
Ca2Mg3Al3Fe3+Si6O22(OH)2
IMA Status:
Approved IMA 1978 (Dana # Added)
Name Origin:
Named for Gustav Tschermak von Sessenegg (1836-1927), Austrian mineralogist.
Physical Properties:
Cleavage:
[110] Perfect
Color:
green, dark green, or black.
Density:
3.14 - 3.35, Average = 3.24
Diaphaniety:
Translucent to Subopaque
Hardness:
5-6 - Between Apatite and Orthoclase
Luster:
Vitreous (Glassy)
Streak:
greenish white
More details...