Vladimirite
| Vladimirite | |
|---|---|
| General | |
| Category | Mineral |
| Formula (repeating unit) | Ca5 [(HAsO4)2 |
| Crystal system | monoclinic |
| Space group | monoclinic |
| Unit cell | V 1,332.98 ų |
| Identification | |
| Formula mass | 848.16 gm |
| Color | pale rose, colorless, white |
| Crystal habit | radial |
| Twinning | penetration |
| Cleavage | good |
| Fracture | fibrous |
| Tenacity | brittle |
| Mohs scale hardness | 3.5 |
| Luster | vitreous(glassy) |
| Streak | white |
| Diaphaneity | transparent |
| Specific gravity | 3.17gm/cc |
| Density | 3.14gm |
| Optical properties | biaxial |
| Refractive index | 1.65-1.66 |
| Birefringence | δ = 0.011 |
| Pleochroism | trichroic |
| References | [1] [7] |
Vladimirite has a general chemical formula of Ca5 [(HAsO4)2|(AsO4)2]·5H2O. It is named after the Vladimirovskoye deposit in Russia, where it was discovered in the 1950s. Vladimirite is a secondary mineral in the oxidized zone of arsenic-bearing mineral deposits. Vladimirite is monoclinic-prismatic, which means crystallographically, it contains three axes of unequal length and the angles between two of the axes are 90 degrees, and one is less than 90 degrees. It belongs to the space group P21/c. The mineral also has an orthorhombic polytype. In terms of its optical properties, Vladimirite is anisotropic which means the velocity of light varies depending on direction through the mineral. Its calculated relief is 1.65-1.661, which is moderate. It is colorless in plane polarized light, and it is weakly pleochroic.
Importance:
Vladimirite has not yet been structurally studied. However, Ferrasite, a polymorph of Vladimirite, has been the subject of several structural and crystal-chemical scientific studies. Ferrasite has peculiar and very complicated dehydration behaviour. It has been proven that Ferrasite dehydrates very slowly in dry air at room temperature. This helps scientist distinguish the mineral from other minerals with the same chemical composition.
References
- ^ Catti, M., Ivaldi, G., Mechanism of the Reaction Ferrasite (Dimorph of Vladimirite) and Structure of the Latter Phase, B 157, 119-130(1981)
- ^ ^Roberts, W.C., Campbell, T.J., and Rapp Jr., G.R. (1990) Encyclopedia of minerals(2nd edition).294p. Library of Congress cataloging, Washington, D.C.
- ^ http://euromin.w3sites.net/mineraux/VLADIMIRITE.html
- ^ http://www.mindat.org/min-4195.html
- ^ http://www.minsocam.org/ammin/AM40/AM40_551.pdf
- ^ http://webmineral.com/specimens/picshow.php?id=2552&target=Vladimirite
- ^ http://webmineral.com/data/Vladimirite.shtml>