Sales did not begin until April because of a 6-month suspension of sales imposed by Congress in response to industry concerns. Conventional identified zinc resources of the world are about 1.8 billion tons. Zinc-bearing coals, mostly in the central United States, also have a resource potential of millions of tons of zinc that could be recovered during coal beneficiation. Aluminum, plastics, and magnesium are major competitors as diecasting materials. Aluminum, steel, and plastics substitute for galvanized sheet.
Many elements are substitutes for zinc in chemical, electronic, and pigment uses.