18mm x 13mm Two UV Reactive Uranium Glass Cabochons

18mm x 13mm UV Reactive Uranium Glass Cabochons Two Cabochons — More available, message for different quantities Size: 18mm x 13mm No chips No cracks Reactive under 395nm* Uranium glass is characterized by the presence of uranium (oxide) and, in some cases, iron oxide. Uranium glass can register above background radiation on a sufficiently sensitive Geiger counter, although most pieces of uranium glass are considered to be harmless and only negligibly radioactive. *PLEASE NOTE: Color of glass and glow may vary slightly from photographs due to variations in screen hues and nm of black light used to produce glow. — The type of Ultraviolet light and the color of visible light is determined by its wavelength. The unit of measurement for light wavelengths is the nanometer (nm). Ultraviolet light is generally considered to be from 200 nm to 400 nm.