The metal's only primordial isotope, bismuth-209, undergoes alpha decay with a half-life about a billion times the estimated age of the universe.

[15][19][20] Bismuth is a brittle metal with a dark, silver-pink hue, often with an iridescent oxide tarnish showing many colors from yellow to blue.

The variations in the thickness of the oxide layer that forms on the surface of the crystal cause different wavelengths of light to interfere upon reflection, thus displaying a rainbow of colors.

[24] Elemental bismuth is denser in the liquid phase than the solid, a characteristic it shares with germanium, silicon, gallium, and water.

[29] At ambient conditions, bismuth shares the same layered structure as the metallic forms of arsenic and antimony,[30] crystallizing in the rhombohedral lattice.

[34] It reacts with nitric acid to make bismuth(III) nitrate (which decomposes into nitrogen dioxide when heated[39]).

[34] The only primordial isotope of bismuth, bismuth-209, was regarded as the heaviest stable nuclide, but it had long been suspected[41] 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 (α) decay half-life of 209Bi to be 2.01×1019 years (3 Bq/Mg),[42][43] over 109 times longer than the estimated age of the universe.

[43] Six isotopes of bismuth with short half-lives (210–215 inclusive) occur in the natural radioactive decay chains of actinium, radium, thorium, and neptunium; and more have been synthesized.

[citation needed] Bismuth forms very few stable bismuthides, intermetallic compounds in which it attains oxidation state −3.

[58][59] The reported abundance of bismuth in the Earth's crust varies significantly by source from 180ppb (similar to that of silver) to 8ppb (twice as common as gold).

Globally, bismuth is mostly produced by refining, as a byproduct of extraction of other metals such as lead, copper, tin, molybdenum and tungsten, though the refining-to-mining ratio depends on the country.

By reacting the molten mixture with chlorine gas the metals are converted to their chlorides while bismuth remains unchanged.

Bismuth has always been produced mainly as a byproduct of lead refining, and thus the price usually reflected the cost of recovery and the balance between production and demand.

[68] Before World War II, demand for bismuth was small and mainly pharmaceutical—bismuth compounds were used to treat such conditions as digestive disorders, sexually transmitted diseases and burns.

Minor amounts of bismuth metal were consumed in fusible alloys for fire sprinkler systems and fuse wire.

During World War II bismuth was considered a strategic material, used for solders, fusible alloys, medications and atomic research.

[68] In the early 1970s, the price rose rapidly due to increasing demand for bismuth as a metallurgical additive to aluminium, iron and steel.

In the early 1990s, research began on the evaluation of bismuth as a nontoxic replacement for lead in ceramic glazes, fishing sinkers, food-processing equipment, free-machining brasses for plumbing applications, lubricating greases, and shot for waterfowl hunting.

[69] Growth in these areas remained slow during the middle 1990s, in spite of the backing of lead replacement by the United States federal government, but intensified around 2005.

[56] Bismuth oxychloride (BiOCl) is sometimes used in cosmetics, as a pigment in paint for eye shadows, hair sprays and nail polishes.

[9][56][83][84] This compound is found as the mineral bismoclite and in crystal form contains layers of atoms (see figure above) that refract light chromatically, resulting in an iridescent appearance similar to nacre of pearl.

[67] Its low toxicity will be especially important for solders to be used in food processing equipment and copper water pipes, although it can also be used in other applications including those in the automobile industry, in the European Union, for example.

Many automatic sprinklers, electric fuses, and safety devices in fire detection and suppression systems contain the eutectic In19.1-Cd5.3-Pb22.6-Sn8.3-Bi44.7 alloy that melts at 47 °C (117 °F)[19] This is a convenient temperature since it is unlikely to be exceeded in normal living conditions.

Before deforming a thin-walled metal part, it is filled with a melt or covered with a thin layer of the alloy to reduce the chance of breaking.

[92][93] Similarly, alloys containing comparable parts of bismuth and lead exhibit a very small change (on the order 0.01%) upon melting, solidification or aging.

[94][95] Some bismuth alloys, such as Bi35-Pb37-Sn25, are combined with non-sticking materials such as mica, glass and enamels because they easily wet them allowing to make joints to other parts.

[96] Scientific literature indicates that some of the compounds of bismuth are less toxic to humans via ingestion than other heavy metals (lead, arsenic, antimony, etc.

[108] Its biological half-life for whole-body retention is reported to be 5 days but it can remain in the kidney for years in people treated with bismuth compounds.

[116][117] This article incorporates text from this source, which is in the public domain: Brown, R. D., Jr. "Annual Average Bismuth Price", USGS (1998).