Zinc is a bit of a mystery. When was the last time you saw a piece of zinc? Unlike copper and aluminum, zinc is hardly ever used on its own. It is used to galvanize steel (preventing rust), to make alloys such as brass and bronze, and in various other chemical applications. One of zinc's most familiar applications, zinc oxide, hardly even seems like a metal. After all, why should a metal be put in a microwavable burrito or used as sunscreen to prevent sunburn? Yet zinc does have these applications. Zinc's unjust lack of recognition has a long history. Despite having been used for more than 5,000 years as an important constituent of brass and, frequently, of bronze, zinc was not recognized as a metal in Europe until the sixteenth century.
PROCESSING AND PRODUCTION
Zinc accounts for roughly 0.007 percent of the Earth's crust on a mass basis, making it only slightly more common than copper.1 Economically, zinc sulfide is the most important mineral form of the metal with mined ores having concentrations from 1 to 15 percent zinc sulfide. These levels of concentration are far from what is required for cost-effective smelting, so zinc undergoes beneficiation to increase the concentration of zinc in the ore.
Beneficiation has two stages. First, the zinc is milled, or crushed, to increase surface exposure. Second, the zinc is separated from other minerals and low value rock (gangue) by froth flotation. Froth flotation refers to the process by which milled ore submerged ...