Field of View: 2.7 mm
Tabular native Bismuth crystals.
Collection and photo: Stephan Wolfsried
Bismuth is an uncommon mineral of arsenic group, composed of the element of the same name. Its rarity is about the same as silver and it is about twice as abundant as gold. It usually forms in ugly masses, though occasionally does form in aesthetic lustrous crystals. Bismuth has a metallic-white color with a slight reddish or pinkish hue. This pure color will only be present on an untarnished (i.e. freshly broken) surface, since Bismuth tarnishes yellow to dark-gray.
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 widely available to collectors, and are sometimes not labelled as being lab grown. It is safe to assume that any hopper-shaped crystal with a fine luster and no tarnish is laboratory-grown.
Although long thought to be stable, bismuth, as an element, was shown to be weakly radioactive, with an enormously long half-life period: 1.9 × 1019 years. Bismuth poisoning can occur and has according to some reports been common in relatively recent times. As with lead, bismuth poisoning can result in the formation of a black deposit on the gums, known as a bismuth line.