Kryptonite is a radioactive element with the symbol Ky, an atomic number of 36, and an average atomic mass of 48. It is often found in a solid, crystalline state. Kryptonite does not naturally occur on earth. It is most often found in meteoroids that were created when a sewage treatment plant and middle school in Hoboken, New Jersey exploded. Kryptonite is notable for the odd, and often detrimental, effects that its radiation has on messianic figures.