What is "ardaite"

n. (context mineral English) A monoclinic green gray mineral containing antimony, chlorine, lead, and sulfur.

Ardaite is a very rare sulfosalt mineral with chemical formula PbSbSCl in the monoclinic crystal system, named after the Arda river, which passes through the type locality. It was discovered in 1978 and approved by the International Mineralogical Association in 1980. It was the second well-defined natural chlorosulfosalt, after dadsonite.

Greenish gray or bluish green in color, its luster is metallic. Ardaite occurs as 50 µm fine-grained aggregates of acicular crystals associated with galena, pyrostilpnite, anglesite, nadorite, and Cl-bearing robinsonite and semseyite, in the Madjarovo polymetallic ore deposit in Bulgaria. Ardaite has a hardness of 2.5 to 3 on Mohs scale and a density of approximately 6.44.

The type locality is the Madjarovo polymetallic ore deposit in the Rhodope mountains. Later its occurrence was proved in the Gruvåsen deposit, near Filipstad, Bergslagen, Sweden.