Bismuthinite

BISMUTHINITE, bismuth glance (EN: bismuthinite, bismuth glance, bismuthine; DE: Bismuthinit; FR: bismuthine; ES: bismutina; RU: висмутин) is the mineral of the subclass of the simple sulfides, Bi2S3. The content of Bi is up to 81%. There often exist the impurities of Pb (up to 5%), Cu (up to 3.2%), sometimes Sb (up to 2.4%), Se (up to 8.8% within the selenium-bismuthinite). Bismuthinite crystallizes into the rhombic crystal systems. There are at the basis of the crystal structure the zigzag-shaped chains of the alternating Bi and S atoms, which are bonded into the ribbons. Bismuthinite forms the elongated grains, granular and radiant aggregates; the columnar (up to acicular) crystals are rare. The colour is tin-white to lead-gray, sometimes with the yellowish or bluish iridescence. The lustre is metallic. Bismuthinite may be cut using the knife. The cleavage is perfect along one direction. The hardness is 3.5. The density is 6800 kilograms per cubic metre.

Bismuthinite is the semiconductor of the n-type with the band gap of 1.2 electron-volts. The electric resistivity varies very much (depending on the impurities), amounting to 5.7•10^2 ohm-metres on average.

Bismuthinite is the hydrothermal mineral; it may be encountered within the veinous tin-tungsten deposits, and within the greisens (Tasna and other places within Bolivia; Karaoba within the Kazakh SSR), within the skarns (Chokadam-Bulak within the Central Asia), within the arsenic-bismuth (Ustarasay within the Central Asia), copper-bismuth, and gold-bismuth deposits, sometimes within the pegmatites. Bismuthinite is characteristic for the tin deposits of Bolivia, and tin-lead-zinc deposits of Japan. Within the zone of the weathering, bismuthinite transitions into the yellow secondary products, namely, the bismuth ochres (oxides, hydroxides, and carbonates of bismuth).

Bismuthinite is the main mineral of the bismuth ores, but the large clusters of bismuthinite are encountered rarely.

The major method for the beneficiation is the flotation. The collectors are: xanthates, Aerofloats ®, and other collectors at the pH of 8-9; the regulator of the environment is soda. The depressors are: sodium sulfide, and sodium sulfite in combination with the copper sulfate, and potassium bichromate. Bismuthinite is separated from the pyrite and arsenopyrite using the cyanide within the alkaline medium. During the extraction of bismuthinite from the complex ores, there are used the combined schemes for the beneficiation using the hydrometallurgy, and also the method for the reverse flotation with the depression of bismuthinite using the sodium sulfide, and with the extraction of the iron and copper sulphides using the cationic collector. At the industrial plants, bismuthinite is mostly extracted into the lead concentrates, and partly into the copper, molybdenum, and tungsten concentrates, from which it is isolated during the pyrometallurgical or hydrometallurgical re-working process. In case of the existence of gold within the ore, there may be conducted the preliminary amalgamation.