Bismuth(III) oxide is a pale yellow solid. It does not dissolve in water. It dissolves in acids to make other bismuth(III) salts. When it is electrolyzed, it makes a bright red solid, bismuth(V) oxide. It has several different crystal structures that have been studied. It reacts with rare earth metal oxides and the products are being studied.
Bismite is the mineral form of bismuth(III) oxide. It is an ore of bismuth. Its Mohs hardness is 4.5 to 5 and its specific gravity is quite high, around 8 or 9. It is made when bismuthinite is oxidized. It was first found in Nevada in 1868.
It can be made by reacting sodium hydroxide with a bismuth(III) salt such as bismuth(III) chloride. It can also be made by igniting powdered bismuth metal. Another way of making it is to react bismuth nitrate (made by dissolving bismuth in nitric acid) with concentrated sodium hydroxide.
Bismuth(III) oxide is used in pyrotechnics to make fireworks that burn with an effect called "dragon's eggs". Lead(II,IV) oxide was used for this in the past, but now is considered too toxic to use. It is also used in research and the making of other bismuth compounds.