Baumstarkite , Miargyrite Locality: San Genaro Mine, Castrovirreyna District , Castrovirreyna Province , Huancavelica Department , Peru ( Locality at mindat.org ) Size: 3.4 x 2.7 x 1.5 cm. This piece consists of rounded crystal-aggregates up to an amazing 1 cm in size. The flattened platy xls are Baumstarkite, a dimorph of miargyrite. The deep charcoal color and metallic luster are very good. The matrix is a mixture of Baumstarkite and Miargyrite. Ex. Charlie Key. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Baumstarkite
Baumstarkite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula Ag₃Sb₃S₆.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Aramayoite structural group.
Key properties: Mohs hardness 2.5; specific gravity 5.33; Grayish red to grayish black streak; Metallic luster.
IMA symbol Bum, IMA status: approved, named in 1999.
Of hydrothermal hypogene origin coating miargyrite (Peru); in an epithermal gold- silver quartz vein cutting black mudstone (Japan).
It is found associated with Miargyrite, pyrargyrite, stannite, kesterite, andorite, diaphorite, robinsonite, galena, chalcopyrite, sphalerite, pyrite (Peru); pyrargyrite-proustite.
The mineral was named to honor Manfred Baumstark (b. 1954), German mineralogist, who provided the type material.