Name/Title
BismuthEntry/Object ID
LN2012.1.9Description
Assemblage Zone: pegmatite dikes
Chemical Composition: Bi
Crystal System: Triclinic System
Description: Common Name: Bismuth (lab created)
Group Name: Element
Chemistry: Bi, bismuth
Location: unknown
Description: Bismuth crystal with many iridescent refraction hues on its oxide surface. This artificially grown bismuth crystal has a stair-step crystal structure.
Physical Properties:
Bismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead. It is a brittle metal with a silvery white color when freshly produced, but is often seen in air with a pink tinge owing to surface oxidation. Bismuth metal has been known from ancient times, although until the 18th century, it was often confused with lead and tin, which each have some of the metal's bulk physical properties.
Bismuth is the most naturally diamagnetic of all metals, and only mercury has a lower thermal conductivity.
Bismuth has classically been considered to be the heaviest naturally occurring stable element, in terms of atomic mass. Recently, however, it has been found to be very slightly radioactive: its only primordial isotope bismuth-209 decays via alpha decay into thallium-205 with a half-life of more than a billion times the estimated age of the universe.
Bismuth has unusually low toxicity for a heavy metal. As the toxicity of lead has become more apparent in recent years, alloy uses for bismuth metal (presently about a third of bismuth production), as a replacement for lead, have become an increasing part of bismuth's commercial importance.
Bismuth is a brittle metal with a white, silver-pink hue, often occurring in its native form with an iridescent oxide tarnish showing many colors from yellow to blue. The spiral, stair-stepped structure of a bismuth crystal is the result of a higher growth rate around the outside edges than on the inside edges. The variations in the thickness of the oxide layer that forms on the surface of the crystal causes different wavelengths of light to interfere upon reflection, thus displaying a rainbow of colors. When combusted with oxygen, bismuth burns with a blue flame and its oxide forms yellow fumes. Its toxicity is much lower than that of its neighbors in the periodic table, such as lead, tin, tellurium, antimony, and polonium.
No other metal is verified to be more naturally diamagnetic than bismuth. It is the most diamagnetic of naturally occurring elements. (Superdiamagnetism is a different physical phenomenon.) Of any metal, it has the second lowest thermal conductivity (after mercury) and the highest Hall coefficient. It has a high electrical resistance. When deposited in sufficiently thin layers on a substrate, bismuth is a semiconductor, rather than a poor metal.
Elemental bismuth is one of very few substances of which the liquid phase is denser than its solid phase (water being the best-known example). Bismuth expands 3.32% on solidification; therefore, it was long an important component of low-melting typesetting alloys, where it compensated for the contraction of the other alloying components.
Though virtually unseen in nature, high-purity bismuth can form distinctive, colorful hopper crystals. It is relatively nontoxic and has a low melting point just above 271 °C, so crystals may be grown using a household stove, although the resulting crystals will tend to be lower quality than lab-grown crystals.
Crystal structure: trigonal
Magnetic ordering: diamagnetic
Electrical resistivity: (20 °C) 1.29 µO·m
Thermal conductivity: 7.97 W·m-1·K-1
Thermal expansion: (25 °C) 13.4 µm·m-1·K-1
Speed of sound (thin rod): (20 °C) 1790 m·s-1
Young's modulus: 32 GPa
Shear modulus: 12 GPa
Bulk modulus: 31 GPa
Poisson ratio: 0.33
Mohs hardness: 2.25
Brinell hardness: 94.2 MPa
Fracture: Uneven
Hardness: 2 Gypsum
Luster: Metallic
Occurrence: In the Earth's crust, bismuth is about twice as abundant as gold. It is not usually economical to mine it as a primary product. Rather, it is usually produced as a byproduct of the processing of other metal ores, especially lead, tungsten (China), tin, copper, and silver (indirectly) or other metallic elements.
The most important ores of bismuth are bismuthinite and bismite. In 2005, China was the top producer of bismuth, with at least 40% of the world share followed by Mexico and Peru, reports the British Geological Survey. Native bismuth is known from Australia, Bolivia, and China.
According to the United States Geological Survey, world 2009 mine production of bismuth was 7,300 tonnes, with the major contributions from China (4,500 tonnes), Mexico (1,200 tonnes) and Peru (960 tonnes). World 2008 bismuth refinery production was 15,000 tonnes, of which China produced 78%, Mexico 8% and Belgium 5%.
The difference between world bismuth mine production and refinery production reflects bismuth's status as a byproduct metal. Bismuth travels in crude lead bullion (which can contain up to 10% bismuth) through several stages of refining, until it is removed by the Kroll-Betterton process or the Betts process. The Kroll-Betterton process uses a pyrometallurgical separation from molten lead of calcium-magnesium-bismuth drosses containing associated metals (silver, gold, zinc, some lead, copper, tellurium, and arsenic). The Betts process takes cast anodes of lead bullion and electrolyzes them in a lead fluorosilicate-hydrofluorosilicic acid electrolyte to yield a pure lead cathode and an anode slime containing bismuth. Bismuth will behave similarly with another of its major metals, copper.
The raw bismuth metal from both process contains still considerable amounts of other metals foremost lead. By reacting the molten mixture with chlorine gas the metals are converted to their chlorides while bismuth remains unchanged. Impurities can also be removed by various other methods for example with fluxes and treatments yielding high-purity bismuth metal (over 99% Bi).
Rock Type: Igneous
Specific Gravity: 9.747
Streak: White
Variety: The only primordial isotope of bismuth, bismuth-209, was traditionally regarded as the heaviest stable isotope, but it had long been suspected to be unstable on theoretical grounds. This was finally demonstrated in 2003, when researchers at the Institut d'Astrophysique Spatiale in Orsay, France, measured the alpha emission half-life of 209 Bi to be 1.9×1019 yr, over a billion times longer than the current estimated age of the universe. Owing to its extraordinarily long half-life, for all presently known medical and industrial applications, bismuth can be treated as if it is stable and nonradioactive. The radioactivity is of academic interest because bismuth is one of few elements whose radioactivity was suspected, and indeed theoretically predicted, before being detected in the laboratory.
Several isotopes of bismuth with short half-lives occur within the radioactive disintegration chains of actinium, radium, and thorium, and more have been synthesized experimentally.
Commercially, the radioactive isotope bismuth-213 can be produced by bombarding radium with bremsstrahlung photons from a linear particle accelerator. In 1997, an antibody conjugate with Bi-213, which has a 45-minute half-life, and decays with the emission of an alpha particle, was used to treat patients with leukemia. This isotope has also been tried in cancer treatment, e.g. in the targeted alpha therapy (TAT) program. Bismuth-213 is also found on the decay chain of uranium-233.Collection
Carol Swisher Mineral-Uses CollectionDimensions
Width
1-13/16 inDepth
1-3/16 inLength
2-7/8 inDimension Notes
Dimension taken at widest pointsLocation
Location
Container
front rowDrawer
centerShelf
topCabinet
Mineral UsesWall
west wallBuilding
Museum Entrance HallwayCategory
Permanent
