ˈkalkəˌsīt noun
( -s )
Etymology: irregular from French chalcosine chalcocite + English -ite — more at chalcosine
: a black or dark gray mineral Cu 2 S of metallic luster consisting of native cuprous sulfide occurring in orthorhombic crystals or massive (hardness 2.5-3, specific gravity 5.5-5.8)