Usovite

General Information:
 Chemical Formula:
Ba2CaMgAl2F14
 Composition:
(Molecular Weight = 658.98 gm)
Barium 41.68 % Ba
Calcium 6.08 % Ca
Magnesium 3.69 % Mg
Aluminum 8.19 % Al
Fluorine 40.36 % F 
 Empirical Formula:
Ba2CaMgAl2F14
 Environment:
Fluorite veins.
 IMA Status:
Approved IMA 1967
 Locality:
Upper Noiby River area, Yenisei region, Siberia, Russia.
 Name Origin:
Named for Mikhail Antonovich Usov (1883-1939), Russian geologist.
Physical Properties:
 Cleavage:
[???] Perfect
 Color:
brown, dark brown, or yellowish brown.
 Density:
4.18
 Diaphaniety:
Translucent to Opaque
 Habits:
Granular - Generally occurs as anhedral to subhedral crystals in matrix., Platy - Sheet forms (e.g. micas).,
 Hardness:
3.5 - Copper Penny
 Luster:
Vitreous - Greasy
 Streak:
white
More details...