Smithsonite

Smithsonite, also known as zinc spar, is the mineral form of zinc carbonate. Historically, smithsonite identified with hemimorphite before it realized that they were two different minerals. The two minerals are very similar in appearance and the term calamine used for both, leading to some confusion. The distinct mineral smithsonite named in 1832 by François Sulpice Beudant in honor of English chemist and mineralogist James Smithson (1765–1829), who first identified the mineral in 1802.

Smithsonite a variably colored trigonal mineral which only rarely found in well formed crystals. The typical habit is as earthy botryoidal masses. It has a Mohs hardness of 4.5 and a specific gravity of 4.4 to 4.5.

It occurs as a secondary mineral in the weathering or oxidation zone of zinc-bearing ore deposits. It sometimes occurs as replacement bodies in carbonate rocks and as such may constitute zinc ore.