Smithsonite was named in honor of James Smith, founder of the Smithsonian Institution.
This mineral belongs to the carbonate group and consists of zinc carbonate ZnCO3. It effervesces in hydrochloric acid. Its streak is white, and it has silky luster, its specific gravity is 4.4–4.5, its hardness is 4.5. Its crystals belong to the trigonal system, but they are rare. Smithsonite commonly occurs in either a globular (botryoidal) or in a massive (granular) form.
It has a wide range of colors because of chemical impurities (listed here in brackets): white to gray [no impurities]; blue, blue-green, to apple green [copper]; yellow [cadmium]; pink to purple [cobalt]; and brown to red [iron].
It often forms as a secondary mineral in the upper oxidation zone of zinc-ore deposits within metamorphic rock complexes. It is found in Greece, Spain, Africa, and the USA (one famous example is at the Kelly Mine in New Mexico).
The two images shown above are of the botryoidal form of an encrustation of smithsonite (38 mm length an 9 mm in height) from the Kelly Mine at Magadalena, Socorro County, central New Mexico.
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