Selenide, galena group, a complete solid solution series exists between galena and clausthalite (AM 44.166-175). Selenium-bearing mineral.
Specific gravity: 7.8 to 8.22
Hardness: 2½ to 3
Colour: Bluish grey to lead-grey
Clausthalite occurs in low-sulphur hydrothermal deposits with other selenides (Webmin) and also in mercury
deposits (HOM); it is
probably of secondary origin in some deposits
Associated minerals include tiemannite, klockmannite, berzelianite, gold, stibiopalladinite, umangite and uraninite (HOM, Mindat).
At Sierra de Umango, Argentina, a massive ore specimen of umangite has been found cut by veinlets of chalcomenite and malachite and having small inclusions of clausthalite (AM 35.337-364).
Also at Sierra de Umango, Argentina, a massive ore specimen of klockmannite has been found cut by veinlets of clausthalite and chalcomenite (AM 35.337-364).
At Coiquechaca, Bolivia, penroseite has been found cut by veinlets of clausthalite (AM 35.337-364).
At Clausthal, Harz mountains, Germany, granular and massive clausthalite has been found embedded in a light silicified rock which contains a few grains of chalcopyrite (AM 35.337-364).
At Tilkerode, Harz, Germany, clausthalite has been found with chalcopyrite in carbonate gangue (AM 35.337-364).
The type locality is the St Lorenz Mine, Clausthal-Zellerfeld, Goslar, Lower Saxony, Germany.
At Tsumeb, Namibia, the little information that is available suggests that clausthalite and umangite may be part of the secondary supergene assemblage rather than the primary hypogene one (R&M 91.6.550).
Common impurities: Hg,Co,Cu
Back to Minerals