Sphalerite is a sulphide mineral with a chemical composition (Zn, Fe) S, which occurs mainly in independent crystalline druses in Trepča. In addition to galena, sphalerite is the most economically important mineral Trepca and serves as the main zinc ore. The example shown in the picture is a variety of sphalerite with a high iron content known as marmatite, which is black and opaque.