Fluorescent and Phosphorescent Minerals
Minerals are able to fluoresce subdued to moderate to even brilliant colors when exposed to ultraviolet light of various wave lengths. Ultraviolet light is beyond the visible range of the human eye. It is associated within the violet wave length in the electromagnetic spectrum. Light between the wave lengths of 320 nanometers to 400 nanometers (nm) is referred to as long wave ultraviolet light. This is UVA and is often referred to as the "Black Light" amongst the hobbyist. UVA can be both a frosted white bulb called "black light" (BL), or the purple bulb, "black light blue" (BLB). If you have ever been to a dance at night where they have used Black Lights, you may have noticed that white colored cotton shirts will glow a brilliant blueish-white color when exposed to black light or black light blue. UVB, the mid-range, is 280-320 nm. Mid-range bulbs are found in 302, 206, and 312 nm. This range of light produces an interesting fluorescence in some minerals. Long wave can be found at 350, 368, and 370 nm. UVC, the short wave range, is below 280 nm. Shortwave ultraviolet light produces beneficial and harmful exposure to the skin. Short and mid-range bulbs are always filtered with special short wave filter glass to reduce visible light. Long wave bulbs can likewise be filtered through long wave filters made of stained glass or exhibitors can use BLB bulbs without filters.
Light to moderate exposure to UVB assists the body in absorbing vitamin D and also causes the skin to tan. The UVC, or short wave length of light causes ionization to take place in the skin. Over exposure can result in painful sunburn and the increased risk of skin cancer.