Clausthalite Locality: Greywacke quarry, Rieder , Gernrode , Harz Mts, Saxony-Anhalt , Germany ( Locality at mindat.org ) Size: 6.5 x 4.8 x 3.5 cm. Clausthalite is a rare lead selenide and this rich specimen hails from near the Type Locality in the Harz Mountains of Germany. Scintillating, metallic clausthalite microcrystals richly cover the front, top and back of this sculptural, mounded carbonate matrix. The carbonate veins at the Greywacke Quarry at Rieder host a variety of rare selenium minerals. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Clausthalite
Lead selenide — the selenium analogue of galena, with which it forms a complete solid-solution series.
Intro adapted from Wikipedia (CC BY-SA).
Clausthalite is an IMA-recognized mineral species in the sulfide class, with the chemical formula PbSe.
It crystallizes in the cubic crystal system (space group Fm3m). It is a member of the Rocksalt structural group.
Key properties: Mohs hardness 2.5–3; specific gravity 7.8–8.22; Grayish black streak; Metallic. R: (400) 63.4, (420) 63.0, (440) 61.8, (460) 60.1, (480) 58.4, (500) 56.7, (520) 55.3, (540) 54.0 luster.
IMA symbol Cth, grandfathered status — known before the IMA’s founding, named in 1832.
Associated in low-sulfur hydrothermal deposits with other selenides, also in mercury deposits. Probably of secondary origin in some deposits.
It is found associated with Tiemannite, klockmannite, berzelianite, umangite, gold, stibiopalladinite, uraninite.
The name is derived from the locality at Clausthal, Germany.