Grey-black microcrystals and veinlets of the very rare Ag-Hg mineral balkanite from one of the few localities known worldwide (Cerro Morita, Naco Municipality, Sonora, Mexico) associated to green brochantite. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Balkanite
Balkanite is an IMA-recognized mineral species in the sulfide class, with the chemical formula Ag₅Cu₉HgS₈.
It crystallizes in the orthorhombic crystal system (space group Pmmm).
Key properties: Mohs hardness 3.5; specific gravity 6.318; Metallic. Anisotropism: Strong. R1 –R2: (400) —, (420) —, (440) 35.4–30.6, (460) 35.6–31.0, (480) 35.4–31.0 luster.
IMA symbol Bkn, IMA status: approved, named in 1971.
Found in high-grade copper ores in a stratiform Pb–Zn–Cu deposit (Sedmochislenitsi deposit, Bulgaria).
It is found associated with Bornite, chalcocite, chalcopyrite, djurleite, digenite, tennantite, stromeyerite, mckinstryite, wittichenite, bismuth, rammelsbergite, mercurian silver.
The name refers to the medieval and popular name of the Stara Planina (Balkan Mountains), the main mountain range giving its name to the Balkan Peninsula.