Smithsonite, or zinc spar, is zinc carbonate ZnCO3, a mineral ore of zinc. Historically, smithsonite was ientified with hemimorphite before it was realised that they were two distinct minerals. The two minerals are very similar in appearance and the term calamine has been used for both, leading to some confusion. The distinct mineral Smithsonite was first described in 1832 and named for British chemist and mineralogist, James Smithson (1754-1829), whose estate financed the Smithsonian Institution.