Alloclasite - Encyclopedia
Class : Sulfides and sulfosalts
Subclass : Sulfides
Crystal System : Monoclinic
Chemistry : (CoFe)AsS
Rarity : Rare
Alloclasite is a rare to very rare mineral present in high temperature cobalt and arsenic hydrothermal deposits, as well as exceptionally in certain silicified metamorphic rocks. Its name comes from the Greek allos (other) and klastos (to break), in reference to its particular cleavage which allows it to be differentiated from similar minerals such as glaucodot and marcasite. Alloclasite is a dimorph of glaucodot ; it constitutes short to elongated prismatic crystals according to [010], frequently striated, and columnar to radiate aggregates forming hemispheres. It has a strong metallic luster, a pewter-white color and a perfect {101} cleavage. It is a very accessory ore of cobalt.
Alloclasite in the World
Twinning
No twin known for this mineral species.
Fakes and treatments
No fake reported for this mineral species.
Hardness : 5
Density : 5,95
Fracture : Irregular to sub-conchoidal
Trace : Black
TP : Opaque
RI : Not measurable
Birefringence : None
Optical character : None
Pleochroism : None
Fluorescence : None
Solubility : Nitric acid
Magnetism : None
Radioactivity : None