Guanajuatite Locality: Santa Catarina Mine, Rancho Calvillo, Santa Rosa , Sierra de Santa Rosa, Municipio de Guanajuato, Guanajuato , Mexico ( Locality at mindat.org ) Size: 2.4 x 1.4 x 1.1 cm. A small specimen of this very rare bismuth selenide species from the Type Locality. Year of Discovery: 1873. This must have ended up in the Bement collection SOON AFTER, in the late 1800s, since the collection was donated in 1910. Ex. American Museum of Natural History , Clarence Bement collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Guanajuatite
Guanajuatite is an IMA-recognized mineral species in the sulfide class, with the chemical formula Bi₂Se₃.
It crystallizes in the orthorhombic crystal system (space group Pnma). It is a member of the Stibnite structural group.
Key properties: Mohs hardness 2.5–3; specific gravity 6.25–6.98; Shiny gray streak; Metallic luster.
IMA symbol Gj, grandfathered status — known before the IMA’s founding, named in 1873.
Found in hydrothermal deposits of low to medium temperatures.
It is found associated with Bismuthinite, bismuth, clausthalite, nevskite, galena, pyrite, calcite.
The name is derived from the locality in Guanajuato, Mexico.