The United States is especially favored in the matter of zinc ores and so is able to produce more of the metal than is any other nation. In New Jersey occurs the mineral, willemite, which yields large quantities of an exceptionally pure metal. In Wisconsin and Missouri are the numerous mines whose ores smelted in the central States afford high-grade metal and make this the leading section of the country. Throughout the west-era States are many other mines, some of them enormously large, whose ores are mixed with minerals of other metals and which yield large tonnages but poorer quality stuff.
Zinc sulphide, ZnS, is the primitive mineral, but the carbonate, ZnCO3, is quite an important mineral, and some silicate and some oxide come to light now and then. The carbonate may be calcined before smelting, although it usually is charged direct into the retorts. The sulphide must be roasted first before being available for reduction. If the ore is not well roasted, it causes serious loss; on this account zinc, ores commonly are roasted far better than are either copper or lead ores.