Clausthalite - Encyclopedia
Class : Sulfides and sulfosalts
Subclass : Selenides
Crystal system : Cubic
Chemistry : PbSe
Rarity : Rare
Clausthalite is a selenide typical of lead-selenium-copper hydrothermal veins, mercury deposits, sometimes uranium deposits, mainly pitchblende-uraninite veins. It is particularly abundant in geological "accidents": hydrothermal veins where the curiously absent sulfur was replaced by selenium. It has a crystal structure identical to galena with which it forms a continuous solid solution. It was named after its discovery location : Clausthal (Germany). Although rare, clausthalite is the most common selenide and is often found in finely grained masses, rarely in small cubic crystals, associated with other selenides, notably copper (eskebornite, berzelianite, etc...) and depending on the deposits, galena, pitchblende or chalcopyrite. Its slightly bluish gray color evokes non-lamellar molybdenite. It is an accessory ore of selenium.
Main photo : Clausthalite from Schlema-Hartenstein mining district, Saxony, Germany © Stephan Wolfsried
Clausthalite in the World
Twinning
No twins known for this mineral species.
Fakes and treatments
No fake identified for this mineral species.
Hardness : 2.5 to 3
Density : 7,8 to 8.2
Fracture : Irregular
Streak : Grey-black
TP : Opaque
RI : -
Birefringence : None
Optical character : None
Pleochroism : None
Fluorescence : None
Solubility : Sulfuric acid and nitric acid
Magnetism : None
Radioactivity : None