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Formula: PbSe
Selenide, galena group, a
complete solid solution series exists between
galena and clausthalite (AM 44.166-175).
Crystal System: Isometric
Specific gravity: 7.8 to 8.22 measured, 8.275 calculated
Hardness: 2½ to 3
Streak: Grey-black
Colour: Bluish grey to lead-grey
Environments
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
(HOM).
Associated minerals include tiemannite,
klockmannite,
berzelianite,
gold, stibiopalladinite,
umangite and uraninite
(HOM, Mindat).
Localities
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
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