April 02, 2014
Photographer: Stan Celestian; Stan's Web site
Summary Authors: Stan Celestian; Jim Foster
The image pair above shows the mineral eucryptite in white light (left) and as exposed to ultraviolet radiation and the resulting intense fluorescence (right). Eucryptite is a "hexagonal lithium aluminium silicate, commonly found as an alteration product of spodumene". This specimen is from a classic pegmatite mine in central Arizona called the Midnight Owl.
Only about 15 percent of all minerals exhibit florescence and most of these minerals will fluoresce in only one color of visible light. Fluorescence is simply the emission of light by a material that temporarily absorbs electromagnetic radiation. The emitted light is typically at a longer wavelength and thus lower energy level than the radiation the material absorbed. When minerals are illuminated by ultraviolet light, they emit in visible light. In a darkened room, the color change can be quite dramatic. Fluorescent lamps are sometimes employed to detect eucryptite and other florescent minerals in mines or caves. Photo taken on December 27, 2013.