Xanthoconite is found as a rare mineral in several of the mines where Proustite is found. One of the few regions to produce relatively large crystals that aren't micros are the Freiberg and Schlema Districts, Erzgebirge, Saxony, Germany. Other good localities include the Lengenbach Quarry, Binn Valley, Wallis, Switzerland; the Imiter Mine, Morocco; San Martín, Zacatecas, Mexico; and the Flathead Mine, Kofford Ridge, Flathead Co., Montana.