Chalcocite

Flambeau Mine, 1000 level, Ladysmith, Rusk County, Wisconsin  USA (1994)

Specimen size: 6.3 × 5.4 × 3.8 cm = 2.48” × 2.13” × 1.50”
Main crystal size: 1.1 × 1 cm = 0.43” × 0.39”