What is "playfairite"

n. (context mineralogy English) A monoclinic-prismatic mineral containing antimony, lead, and sulfur.

Playfairite is a very rare sulfosalt mineral with chemical formula PbSbS in the monoclinic crystal system, named after the Scottish scientist and mathematician John Playfair. It was discovered in 1966 by the Canadian mineralogist John Leslie Jambor. Lead gray to black in color, its luster is metallic. Playfairite shows strong reflection pleochroism from white to brownish gray. Playfairite has a hardness of 3.5 to 4 on Mohs scale and a density of approximately 6.44.

The type locality is Taylor Pit (Concession XIV; Lot 13), Huntingdon Township, Madoc Area, Hastings Co., Ontario, Canada. Small deposits have also been found in Les Cougnasses Mine, Orpierre, Hautes-Alpes, Provence-Alpes-Côte d'Azur, France, Khaidarkan Sb-Hg deposit (Chaidarkan), Fergana Valley, Alai Range, Osh Oblast, Kyrgyzstan and Reese River District, Lander Co., Nevada, US.