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Mass of Natural Bismuth Crystals

The Mineral bismuth




Bismuth has a metallic-white color with a slight reddish or pinkish hue. Such a color will only be present on an untarnished (i.e. freshly broken) surface, since Bismuth tarnishes yellow to dark-gray. Bismuth is not a common mineral and usually occurs in uninteresting forms. It rarely occurs in decent crystals. Bismuth is about as rare as Silver.

Most marketed Bismuth specimens are laboratory grown, and exhibit a very interesting shape. They have hopper-like growths in pseudocubic crystals, and are usually coated with chemicals to prevent tarnish, thus maintaining the silver-white color. Sometimes the coating gives a colorful effect on the bismuth. These artificial crystals are very often sold to collectors without being specified that they are lab grown. Any hopper-shaped crystal with a fine luster and no tarnish should be assumed to be artificial.
Chemical Formula Bi
Composition Bismuth, usually with traces of arsenic, antimony, and sulfur
Variable Formula (Bi,As,Sb,S)
Color Silver-white, sometimes with reddish hue. Oxidizes yellowish to dark gray.
Streak Silver-white
Hardness 2 - 2.5
Crystal System Hexagonal
Crystal Forms
and Aggregates
Crystals are rare, and are usually flat hexagons occurring in parallel groupings. Pseudocubic, hopper-like crystal groupings are almost never found in nature, but are easily grown in a lab. Bismuth also occurs massive and as waterworn nugget in stream beds.
Transparency Opaque
Specific Gravity 9.7 - 9.8
Luster Metallic
Cleavage 2,1 - prismatic ; 3,1 - basal
Fracture Hackly to uneven
Tenacity Brittle and slightly sectile
Other ID Marks 1) Tarnishes yellow to dark gray.
2) Usually striated on cleaved surfaces.
Complex Tests Becomes slightly malleable when heated, expands when solidifying, and is strongly diamagnetic
In Group Native Elements; Semi-Metallic Elements
Striking Features Color, tarnish, sectility, and striations on cleaved surfaces
Environment In mesothermal veins, in hydrothermal replacement deposits, and in granite pegmatites.
Rock Type Igneous, Metamorphic
Popularity (1-4) 2
Prevalence (1-3) 1
Demand (1-3) 2

Bismuth ON EBAY
OTHER NAMES
Native Bismuth


USES
Bismuth is an ore of the element bismuth. Much of the poor quality Bismuth specimens are artificially regrown to produce interestingly shaped hopper-like Bismuth specimens for collectors.

Bismuth has a very interesting property in that it expands when it solidifies, unlike all other matter which contracts. (This same property is exhibited in water.) This unique propery, and the fact that it is highly diamagnetic, offer it numerous uses in the electronics field.

NOTEWORTHY LOCALITIES
Probably the best specimens were found in Schneeberg and the surrounding areas in the Erzgebirge in Saxony, Germany. Very good specimens have also come from St. Ives, Cornwall, England; Wolfram Camp, Dimbulah, Queensland, Australia; and the Siglo Veinte Mine (Llallagua), Potosi, Bolivia. In Canada, it has been found in and around Cobalt, Timiskaming District, Ontario. It occurs with Bismuthinite in the El Carmen Mine in Durango, Mexico.

COMMON MINERAL ASSOCIATIONS
Bismuthinite, Cassiterite, Quartz

DISTINGUISHING SIMILAR MINERALS
Antimony, Arsenic - lighter (5.6 - 5.7 and 6.6 - 6.7), harder (3 - 3½ and 3½)
Tellurium - lacks reddish hue, lighter color, less dense (6.1 - 6.3)


bismuth PHOTOS
 
ADDITIONAL RESOURCES
 
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