What is "berthierite"

Berthierite \Ber"thi*er*ite\, n. [From Berthier, a French naturalist.] (Min.) A double sulphide of antimony and iron, of a dark steel-gray color.

n. (context mineral English) A steel-gray opaque mineral, with chemical formula FeSb₂S₄.

Berthierite is a mineral, a sulfide of iron and antimony with formula FeSbS. It is steel grey in colour with a metallic lustre which can be covered by an iridescent tarnish. Because of its appearance it is often mistaken for stibnite.

It was discovered in France in 1827 and named for the French chemist, Pierre Berthier (1782–1861).