chalcocite
noun
chal·co·cite ˈkal-kə-ˌsīt 
: a black or gray lustrous metallic mineral that consists of a sulfide of copper and is an important copper ore
Example Sentences
Recent Examples on the Web Materials like the copper ore mineral chalcocite and fool's gold, pyrite, are sulfidic anions. 
David Grossman, Popular Mechanics, 9 Apr. 2018
David Grossman, Popular Mechanics, 9 Apr. 2018 Word History
Etymology
alteration of chalcosine, from French, irregular from Greek chalkos
First Known Use
1868, in the meaning defined above