Bismuth

bismuth

bismuthinite

pegmatite

hydrothermal

Images

Formula: Bi
Native element, arsenic group
Specific gravity: 9.7 - 9.8
Hardness: 2 to 2½
Streak: Lead grey
Colour: Silver white
Solubility: Slightly soluble in hydrochloric acid, readily soluble in sulphuric and nitric acid
Common impurities: Fe,Te,As,S,Sb
Environments:

Pegmatites
Metamorphic environments
Hydrothermal environments

Bismuth occurs in pegmatites and as an unaltered primary mineral in hypothermal (high temperature), tin ore veins. It is widespread, although not in large amounts, in contact metamorphic formations, where it generally occurs in chalcopyrite aggregates, and more rarely in arsenopyrite (Ramdohr p379-380).
In pegmatites associated minerals include chalcopyrite, pyrrhotite, arsenopyrite, pyrite, bismuthinite, molybdenite, sphalerite, galena, wolframite and cassiterite, as well as cubanite and cobaltite.
In vein deposits associated minerals include skutterudite, safflorite, löllingite, bismuthinite, silver, nickeline and breithauptite (Ramdohr p379-380).

Localities

The Needle Hill Mine, Needle Hill, Sha Tin District, New Territories, Hong Kong, China, is a tungsten mine, abandoned in 1967. The principal ore is wolframite, and the principal gangue mineral is quartz. Molybdenum also occurs. The mineralisation consists of a series of parallel fissure veins that cut through granite. Wolframite and quartz are the main minerals, but galena, sphalerite, pyrite, molybdenite and fluorite have also been found here (Geological Society of Hong Kong Newsletter 9.3.29-40). The quartz-wolframite veins are of high-temperature hydrothermal formation, and grade into wolframite-bearing pegmatites.
Wolframite is almost always associated with molybdenite. Other associated minerals found occasionally include pyrite, chalcopyrite, arsenopyrite, sphalerite, bismuth, fluorite, topaz and cassiterite (Hong Kong Minerals (1991). Peng, C J. Hong Kong Urban Council)

At Johanngeorgenstadt, Erzgebirgskreis, Saxony, Germany, native bismuth was among the most important products of the mines. Bismuth generally occurred as fine disseminations in quartz and chert-rich veins, and as impregnations in the country rock. More rarely it was found as massive granular to leafy aggregates, and as intergrowths with cobalt and nickel ores. The feathery to herring-bone habit so well-known at Schneeberg was rare but formed specimens of exceptional beauty; feathery crystal aggregates to 6 cm were found with pitchblende, reddish brown chert or dolomite. Bismuth specimens from the Gewerken Hoffnung mine are particularly rich and fine. Small bismuth crystals, an extreme rarity, were found in the Gabe Gottes and Gottes Segen mines (MinRec 55.5.590).
Bismuth from Johanngeorgenstadt - Image

At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, bismuth has been found as 1-2 mm grains, often coated with beyerite and associated with bismuthinite. The Emmons pegmatite is an example of a highly evolved boron-lithium-cesium-tantalum enriched pegmatite (R&M 94.6.505).

Bismuth-bearing minerals include:

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