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www.mineralgallery.co.za Minerals P-T |
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Smithsonite |
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Name
Smithsonite
Chemistry
ZnCO3
Uses
It is an ore of zinc and a mineral specimen
Color
Blue to green to white or gray
Hardness
5.5
Specific gravity
4.3-4.5
Crystals
Trigonal.
Accompanied by:
Zinc minerals.sphalerite,galena and calcite.
Fracture
Uneven.
Luster
Vitreous.
Cleavage
Rhombohedral perfect.
Streak
White.
Similar to:
Calcite
The zinc carbonate mineral smithsonite is an ore of zinc, formed by oxidation of sphalerite.
It occurs as rounded, crystalline crusts and granular or honeycombed masses that have a vitreous luster and are typically dirty brown or gray in color, and less often white or of a greenish or bluish hue and even pink Smithsonite is found with galena and sphalerite in veins and beds, especially in limestone regions.
Smithsonite at Tsumeb
Smithsonite is the most abundant secondary zinc mineral at Tsumeb. Large masses and botryoidal crusts are relatively common; crystals of rhombohedral to scalenohedral habit reach several cm in size and are the finest in the world. Relatively pure smithsonite is colorless to pale gray. Blackish crystals are filled with inclusions of sulfides.
Cadmiumzinkspath? (Cd-var?) (Zn,Cd)CO3? Smithsonite with up to 5% CdCO3 has been observed elsewhere,and there may be a complete series to otavite.The most obvious smithsonite at Tsumeb is bright yellow being cadmium-rich,but this may be from inclusions of greenoctite. Crystals reach several cm.
Cobalt-smithsonite(Mn-var.)(Zn,Co)CO3 Forms pale pink to brilliant rose-colored crystals in simple rhombohedrons and rarely other habits. Cobaltsmithsonite is probably part of a continuous series to sphaerocobaltite (CoCO3)(not yet reported from Tsumeb). The rhombohedral faces tend to bulge out slightly and are nearly always frosty...
Herrerite (Cuprosmithsonite)(Cu-var)(Zn,Cu)CO3 Herrerite containing up to 3% CuCO3 has been observed. This brilliant green variety has long been a popular mineral from Tsumeb. The crystals range from a frosty apple-green to a nearly adamantine emerald green. One rare specimen is a brilliant turquoise-blue. Crystals commonly exceed 1 cm.
- Mangano-smithsonite(Mn-var) (Zn,Mn)CO3 This variety is also pink although not as brilliant as cobaltsmithsonite.
