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a mineral of the class of simple oxides. Zincite, with the chemical composition ZnO, usually contains admixtures of MgO (up to 9 percent), PbO (up to 5.3 percent), and FeO (up to 1.1 percent). It crystallizes in the hexagonal system. It usually occurs in the form of granular aggregates; zincite crystals are rare. The color ranges from orange-yellow to dark red. The hardness on Mohs’ scale is 4–5, and the density is 5,640–5,680 kg/m3. A semiconductor, zincite is found in recrystallized limestones of contact metasomatic deposits, in which it is associated with willemite, franklinite, and other rare minerals. Zincite is mined in the USA, at Franklin, N.J., as a zinc ore. It has also been discovered in several lead-zinc deposits.