Cuprous selenide, Cu₂Se

The Cuprous selenide, Cu₂Se occurs as the mineral berzelianite. It is produced by direct combination of copper and selenium-vapour, and is a dimorphous substance of steel-grey colour, the transition-point for the two forms being 110° C. At 20° C. its specific heat is 0.1047, and its heat of formation 20.8 Cal.