Kryptonite is no longer the stuff of comic books and Superman movies - it really exists. A newly discovered mineral has been found to contain exactly the same elements as the large green crystals that rob the super-hero of his powers.

Unlike fictional kryptonite, the real thing at London's Natural History Museum is white and powdery, emits no radiation, and comes from Serbia rather than space.

But scientists who analysed the find were astonished to discover that its chemical composition matched a description of kryptonite in the film Superman Returns. When Superman's arch enemy Lex Luthor steals a kryptonite rock fragment from Metropolis Museum, the case containing it is labelled with the words "sodium lithium boron silicate hydroxide with fluorine".

Dr Chris Stanley, a mineralogist at the Natural History Museum, said: "I searched the web using the mineral's chemical formula - sodium lithium boron silicate hydroxide - and was amazed to discover that same name written on a case of rock stolen by Lex Luthor. It does not contain fluorine and is white rather than green, but in all other respects matches that of kryptonite."

Tempting though it might have been to christen the new mineral kryptonite, scientists opted for the name jadarite. The sample can be seen at the Natural History Museum in free events tomorrow and on May 13.

------- From the Daily Telegraph