Conichalcite - Encyclopedia
Class : Phosphates, arsenates, vanadates
Subclass : Anhydrous arsenates
Crystal system : Orthorhombic
Chemistry : CaCu(AsO4)(OH)
Rarity : Uncommon
Conichalcite is a fairly common secondary arsenate from the oxidation zone of arsenic-rich copper deposits, associated with tyrolite, lavendulanite and olivenite. Its name comes from the Greek konis (dust) and khalkos (copper) in reference to its habitus and its chemical composition. Its crystals are extremely rare and always tiny, short prismatic, or isometric. Conichalcite generally appears in bright submillimeter globules and botryoidal or nipple-like encrustations with a fibroradiated structure. Its color, apple green, grass green, or pistachio green, is characteristic.
Main photo : Conichalcite from Gold Hill Mine, Utah, USA © Stephan Wolfsried
Conichalcite in the World
Twinning
A rare twin is known on {001}.
Fakes and treatments
No fake identified for this mineral species.
Hardness : 4.5
Density : 4.33
Fracture : Irregular
Streak : Green
TP : Translucent to transparent
RI : 1.778 to 1.846
Birefringence : 0.034
Optical character : Biaxial (+/-)
Pleochroism : Visible
Fluorescence : None
Solubility : Nitric acid and hydrochloric acid
Magnetism : None
Radioactivity : None