General Information:
Chemical Formula:[ ]Na2(Fe++3Fe+++2)Si8O22(OH)2
Composition:(Molecular Weight = 935.90 gm)Sodium 4.91 %
NaIron 29.84 %
FeSilicon 24.01 %
SiHydrogen 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...
