matildite
/məˈtɪldʌɪt/Mineralogy
noun
A trigonal sulphide of silver and bismuth, AgBiS2, usually occurring as grey to black granular masses that are opaque with a metallic lustre.
Origin
Late 19th century; earliest use found in Edward Dana (1849–1935), mineralogist and physicist. From Italian matildite from Matilda, the name of a mine near Morococha in the department of Junín in central Peru + -ite.