Sternbergite , Pyrargyrite Locality: Jáchymov (St Joachimsthal) , Jáchymov (St Joachimsthal) District, Krušné Hory Mts (Erzgebirge), Karlovy Vary Region , Bohemia (Böhmen; Boehmen) , Czech Republic ( Locality at mindat.org ) EYE-VISIBLE crystals of sternbergite line 80% of the top ridge of this remarkable old specimen, which I received at Tucson in exchange from Bill Pinch. It is a large and very rich specimen for this rare silver species! The crystals are to 1 mm (though most are smaller than that and are sparkly sub-mm crystals), and although the species gets bigger it is but rarely and seldom in any large clusters as we see here. There are literally hundreds of crystals here and the piece could easily be chopped in portions for sale at higher prices in total. Comes with old label from Schortmann's Minerals (1940's). 13 x 7 x 3.5 cm — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Sternbergite
Sternbergite is an IMA-recognized mineral species in the sulfide class, with the chemical formula AgFe₂S₃.
It crystallizes in the orthorhombic crystal system (space group Ccmb). It is a member of the Cubanite structural group.
Key properties: Mohs hardness 1–1.5; specific gravity 4.1–4.21; Black streak; Metallic, brilliant on {001} luster.
IMA symbol Srn, grandfathered status — known before the IMA’s founding, named in 1827.
Found in hydrothermal veins with other silver sulfosalt minerals and in Co–Ni–Ag sulfide assemblages.
It is found associated with Stephanite, acanthite, proustite, pyrargyrite, argentopyrite, xanthoconite, pyrite, galena, sphalerite, dolomite, calcite, quartz.
The mineral was named to honor Caspar Maria Sternberg (1761–1838), Czech botanist, of the National Museum in Prague, Czech Republic.