General Information:
Chemical Formula:
(Al,Fe+++)1.3(V++++,Fe)8O20·4.7(H2O)
Composition:
(Molecular Weight = 858.38 gm)
Aluminum 3.14 % Al
Vanadium 44.51 % V
Iron 5.20 % Fe
Hydrogen 1.10 % H
Oxygen 46.04 % O
Empirical Formula:
AlFe3+0.3V4+7.5Fe3+0.5O204.7(H2O)
IMA Status:
Approved IMA 1963
Locality:
Kurumsak area, Kazakhstan.
Name Origin:
Named for Ivan I. Bok, (1898-), Kazakh mineralogist.
Physical Properties:
Cleavage:
[???] Perfect
Color:
black.
Density:
2.97 - 3.1, Average = 3.03
Diaphaniety:
Opaque
Habits:
Reniform - "Kidney like" in shape (e.g.. hematite)., Encrustations - Forms crust-like aggregates on matrix., Radial - Crystals radiate from a center without producing stellar forms (e .g. stibnite)
Hardness:
3 - Calcite
Luster:
Metallic - Dull
Streak:
brownish black
More details...