Located at the center of our laser etched atomic logo is a crystal of autunite (hydrated calcium uranyl phosphate), which is nearly 50 percent uranium by weight. Under the illumination of the included ultraviolet lights, the crystals glow a striking bright green. Caution! This product is mildly radioactive and the handling instructions are as follows. Do not leave the medallion in direct contact with skin for more than 133 hours per year according to the limits imposed by the Nuclear Regulatory Commission [100 mrem/yr], and do not attempt to extract the uranium from the sealed epoxy resin. Most of the radiation produced is safely contained within the resin, and radiation levels are nearly undetectable at distances greater than one foot.