Veins of quartz containing chalcocite and galena were reported cutting Keweenawan basalt just south of the Douglas Fault in SE sec. Thin coatings and veins of sooty chalcocite are found as a secondary supergene mineral coating chalcopyrite at the Crandon deposit near Little Sand Lake SE Sec. History Survey files, Heyl et. Chalcocite was locally mined near Mineral Point in Sec. Chalcocite was mined in theSE NW Sec.36 T.2N R.3E, about 4 miles NW of Gratiot.
Associated minerals are copper, bornite and chalcopyrite.
It is found in vesicles and the ground mass of Keweenawau volcanic rocks such as at SE SE NW Sec. Chalcocite was abundant at the Flambeau Mine, sec. 9 T.34N. R.6W., south of Ladysmith, where it occurred in a wide variety of habvits, some of world-class specimen quality. It was found generally as sooty to coarsely crystalline granular masses in the supergene zone,where it formed one of the mine's primary ore materials. It was associated with chalcopyrite, malachite, azurite, bornite and pyrite.