Rainbow fluorite: Rainbow fluorite is a type of fluorite that exhibits a range of colors, often in a rainbow-like pattern. It is formed when fluorite crystals are exposed to certain types of radiation, such as ultraviolet light. The radiation causes the fluorite to fluoresce, or emit light of a different color. The colors that are emitted depend on the type of radiation and the impurities that are present in the fluorite. These elements absorb ultraviolet light and re-emit it as visible light, causing the fluorite to glow in a rainbow of colors.