naumannite
/ˈnaʊmənʌɪt/ /ˈnɔːmənaɪt/Mineralogy
noun
Native silver selenide, Ag2Se, crystallizing in the orthorhombic system and usually occurring as black metallic cubes.
Origin
Mid 19th century; earliest use found in James Nicol (1810–1879), geologist. From German Naumannit from the name of Karl F. Naumann, German mineralogist + -it -ite.