Smithsonite

Formula: ZnCO3

Colour: White, grey, yellow, green to apple-green, blue, pink, purple, bluish grey, and brown; colourless or faintly tinted in transmitted light.

Lustre: Vitreous, Pearly

Hardness: 4 – 4½

Specific Gravity: 4.42 – 4.44

Crystal System: Trigonal

Member of: Calcite Group. Siderite-Smithsonite Series.

Name: Lapis calaminaris was a name used by Agricola in 1546. In 1747, Johan Gottschalk Wallerius (Vallerius) used the simplified form calamine for the zinc carbonate. In 1780, Torbern Bergmann analyzed calamines and found they were mixed ores of zinc carbonates and silicates. In 1803, James Smithson made a systematic investigation of calamines and showed that ores identified as calamine consisted of several different minerals: a carbonate and a silicate. The carbonate “calamine” was re-named smithsonite in 1832 by François Sulpice Beudant in honor of James Smithson [1754-1829], British chemist, mineralogist, and benefactor of the Smithsonian Institution (Washington, DC, USA).

Smithsonite is often found as a secondary mineral in the oxidation zone of zinc ore deposits. It can also be observed in sedimentary deposits and as a direct oxidation product of sphalerite.