Two sharp metallic crystals of the extremely rare mineral quadratite from the type and only known locality worldwide (Lengenbach Quarry, Binntal, Wallis, Switzerland). In the main crystal we can see part of the typical octogonal shape of the mineral). The specimen was found in 1998. Quadratite is one the rarest minerals from Lengenbach. — Photo: David Hospital · CC BY-SA 4.0
Quadratite
Quadratite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula AgCdAsS₃.
It crystallizes in the tetragonal crystal system (space group P4_322). It is a member of the Quadratite structural group.
Key properties: Mohs hardness 3; specific gravity 5.31; Reddish brown streak; Metallic in thick laminae luster.
IMA symbol Qd, IMA status: approved, named in 1994.
Found in cavities in hydrothermally altered dolostone, likely formed at a late stage.
It is found associated with Galena, jordanite, pyrite, sphalerite, lengenbachite, hatchite.
Alludes to the characteristic crystal habit.