The minerals in some types of stone have properties which cause them, under certain conditions, to glow or fluoresce. This property can sometimes be beneficial. When searching for the minerals using ultraviolet light these stones will stand out from the other rocks. Some of these stones are prized for the attractive glows they emit.
The mineral autunite fluoresces a yellow-green color. It is composed of the elements calcium, uranium, phosphorus, hydrogen and oxygen. It gains its name from Autun, the town in France near where it was first discovered and where it is common. The mineral is also strongly radioactive.
The mineral fluorite can fluoresce with many colors, blue being the most common, but shades of yellow, green, white, red and purple also occurring. It is naturally colorful even when not fluorescing and is made up of the elements calcium and fluoride.
The mineral calcite, under UV light, will fluoresce both green and reddish-orange. Its natural colors vary between white, yellow, pink and brown when not fluorescing. Calcite is composed of calcium, carbon and oxygen. The mineral is common in South America.
The mineral scapolite can fluoresce as pink, yellow or orange. It is composed of calcium, sodium, aluminium, chlorine, silicon and oxygen. It occurs in Africa, Canada and Asia.
The mineral hyalite fluoresces bright green under UV light. It is a clear, glassy form of opal composed of silicone, hydrogen and oxygen. Like most opal types, it can occur worldwide in rocks with a high silica content.