Stalactites, stalagmites and other cave formations fluoresce under the glow of ultraviolet or blacklight at Poole’s Cavern, Derbyshire, England. Fluorescent formations absorb and release energy very quickly. When an ultraviolet, or black light, is directed at these deposits the manganese molecules become activated and we see the calcite release light as a blue-green glow because it is at a different wavelength than the surrounding light sources. Once the light is removed the glow on the rock disappears.