SMITHSONITE MINERAL FACTS Nevada Turquoise gem stones
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Smithsonite Mineral Facts:

Chemical Formula: ZnCO3: Zinc Carbonate. 64.8% Zinc Oxide by weight

Colors: May be some shade of green, yellow, blue pink, white or colorless. Streak is white.

Hardness: 4.0 to 4.5
Hardness varies somewhat depending on formation and impurities.

Density: 4.3 to 4.45

Cleavage: One perfect cleavage.

Crystallography: Rhombohedral

Luster:. Vitreous luster.

Optics: (Refractive Index): w = 1.850; e = 1.623


Composition, Structure and Associated Minerals:
 Smithsonite is a zinc ore of secondary origin. Found in connection with zinc deposits near the surface, and where the oxidized ores have been acted upon by carbonated waters. Common in connection with zinc deposits lying in limestone rocks. Associated with sphalerite, galena, calamine, cerussite, calcite, limonite, etc. Often found in pseudomorphs after calcite. "Dry-bone ore" is a honeycombed mass, with the appearance of dried bone, whose structure has resulted from the manner of deposition of the mineral.

Smithsonite is rarely well crystallized. It often appears as druses, botryoidal and stalactitic masses, as granular aggregates and as a friable earth. Smithsonite usually contains iron and manganese carbonates, often small quantities of calcium and magnesium carbonates (pink varieties) and sometimes traces of cadmium (yellow varieties).

Identification and Diagnostics
Positive reactions for zinc, its hardness (4.5) and its high specific gravity, together with the effervescence of the mineral in hot hydrochloric acid distinguish smithsonite from all other compounds.

Occurrence, Localities and Origins:
Smithsonite occurs in beds and veins in limestones, where it is associated with galena and sphalerite. It is especially common in the upper, oxidized zone of veins of zinc ores and as a residual deposit covering the surface of weathered limestone containing zinc minerals.

Localities. The mineral is found at Nerchinsk, Siberia; Bleiberg, in Carinthia; Altenberg, Aachen; Province of Santander, Spain; at Mendip Hills (Somersetshire), Matlock (Derbyshire), Alston Moor (Cumberland), Lead Hills (Scotland), and other places in England; at Donegal, in Ireland. and in many lead and zinc mining centers.

In the US at Lancaster, Penn.; at Dubuque, Iowa; in Lawrence and Marion Counties,Arkansas; and in the lead districts of Wisconsin and Missouri.The Wisconsin and Missouri localities are the most important ones in North America.

Smithsonite forms pseudomorphs after sphalerite and calcite and is pseudomorphed by quartz, limonite, calamine and goethite. Found at times in translucent green or greenish blue material which is available for ornamental uses. Such smithsonite is found at Laurium, Greece, and at Kelly, New Mexico. Smithsonite  is a minor ore of zinc; commercially.  Named in honor of James Smithson (1754-1829), who also founded the Smithsonian Institution at Washington.

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New Mexico Smithsonite
Kelly Mine Smithsonite
 

 

Please note that the author, Chris Ralph, retains all copyrights to this entire document and it may not be reproduced, quoted or copied without permission.

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