Superman is most vulnerable to green Kryptonite , mineral debris from Krypton transformed into radioactive material by the forces that destroyed the planet . Exposure to green Kryptonite radiation nullifies Superman 's powers and immobilizes him with pain and nausea ; prolonged exposure will eventually kill him . The only substance on Earth that can protect him from Kryptonite is lead , which blocks the radiation . Lead is also the only known substance that Superman can not see through with his x-ray vision . Kryptonite was introduced in 1943 as a plot device to allow the radio - serial voice actor , Bud Collyer , to take some time off . Although green Kryptonite is the most commonly seen form , writers have introduced other forms over the years : such as red , gold , blue , white , and black , each with its own effect .

Question: element named after fictional planet from which superman came
Answer: Kryptonite