General Information:
Chemical Formula:
[ ]Na2(Fe++3Fe+++2)Si8O22(OH)2
Composition:
(Molecular Weight = 935.90 gm)
Sodium 4.91 % Na
Iron 29.84 % Fe
Silicon 24.01 % Si
Hydrogen 0.22 % H
Oxygen 41.03 % O
Empirical Formula:
Na2Fe2+3Fe3+2(Si8O22)(OH)2
Environment:
Magmatic and metamorphic rocks.
IMA Status:
Approved IMA 1978
Locality:
Granites of Nigeria West Australia. Changaj Hills, Mongoloia.
Name Origin:
Named after the German traveler, E. Riebeck (1853-1885).
Physical Properties:
Cleavage:
[110] Perfect, [???] Perfect
Color:
blue, black, or dark green.
Density:
3.4
Diaphaniety:
Translucent to subtranslucent to opaque
Habits:
Striated - Parallel lines on crystal surface or cleavage face., Fibrous - Crystals made up of fibers., Massive - Fibrous - Distinctly fibrous fine-grained forms.
Hardness:
4 - Fluorite
Luminescence:
Non-fluorescent.
Luster:
Vitreous - Silky
Streak:
greenish brown
More details...