Cosalite - Encyclopedia
Class : Sulfides and sulfosalts
Subclass : Sulfosalts
Crystal system : Orthorhombic
Chemistry : Pb2Bi2S5
Rarity : Uncommon
Cosalite is a relatively common mineral found in mid-temperature Pb-Bi hydrothermal veins and contact metamorphism deposits. It owes its name to its discovery location : the Nuestra Señora mine near Cosala (Mexico). It sometimes appears in prismatic crystals, frequently fibrous to acicular and capillary by elongation according to [001], but most often remains massive, constituting fibrous or feathery aggregates with a radiated texture. With a metallic luster, cosalite has a lead gray to steel gray color. It is an occasional bismuth ore.
Main photo : Cosalite from Luserna Stone Quarries, Piedmont, Italy © Beppe Finello
Cosalite in the World
Right photo : Cosalite de Lauriéras, Saint-Yrieix-la-Perche, Haute-Vienne, France © Pierre Le Roch
Twinning
No twin known for this mineral species.
Fakes and treatments
No fake identified for this mineral species but can be difficult to visually differentiate from other metallic minerals.
Hardness : 2.5 to 3
Density : 6.8 to 7
Fracture : Irregular
Streak : Black
TP : Opaque
RI : -
Birefringence : -
Optical character : -
Pleochroism : None
Fluorescence : None
Solubility : Nitric acid
Magnetism : None
Radioactivity : None