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(named for its discoverer, the Italian chemist N. Covelli, 1790–1829), a mineral of the sulfide class. Chemical composition, CuS; it contains 66.48 percent Cu and 33.52 percent S. The structure of covellite has Cu+ and Cu2+ atoms, as well as the simple ion S2– and the paired ion S22–. The structural elements of Cu2+ surrounded by three S2– and Cu+ ions, which are in the centers of paired tetrahedrons connected by S22 ions, are located in layers and provide the perfect cleavage of covellite. Thus, the structurally regular formula for covellite will be (Cu2S#x00B7;CuS2). Crystals are very rare; secondary incrustations, as well as films on other sulfides or powdery masses that replace them, are common. The color is dark blue. Hardness on the mineralogical scale, 1.5–2.0; density, 4,590–4,670 kg/m3. Covellite is a typical mineral in the zone of secondary sulfide enrichment in the oxidized parts of sulfide copper deposits. It is used as a copper ore.