General term describing any mineral capable of giving off light when put under certain conditions. Three examples of minerals that are luminescent are minerals that exhibit fluorescence, triboluminescence, and thermoluminescence.
The condition of a stamp or postal stationery which has been treated with chemicals which are sensitive to and glow under ultraviolet (UV) light. This permits automatic cancelling equipment to detect the position of the postage on the cover and to orient it for rapid mechanical cancelling.
Said of materials applied on markers (s.) and/or hands (s.), emitting the luminous energy previously absorbed as electromagnetic light rays. Tritium is no longer used and was replaced by other substances having the same emitting powers, but with virtually zero radioactivity, such as Super-LumiNova and Lumibrite.