Bad news for Superman

In a sucker punch to any Men of Steel who'd become complacent in the belief that Kryptonite was a fictional substance, a group of scientists has discovered the Supes-killing rock here on Earth. Mineral experts from the Natural History Museum and Canada's National Research Council found that a previously unidentified substance discovered in Serbia had the same chemical composition as Kryptonite.

Although the mineral shares the chemical formula "sodium lithium boron silicate hydroxide" given in Superman Returns, however, Earth-style Kryptonite is neither green, extra-terrestrial or radioactive - instead it's white and powdery, which we have to admit is a bit of a disappointment.

"Towards the end of my research, I searched the web using the mineral's chemical formula and was amazed to discover that same scientific name written on a case of rock containing Kryptonite stolen by Lex Luther from a museum in the film Superman Returns," explains the Natural History Museum's Dr Chris Stanley. "The new mineral does not contain fluorine and is white rather than green, but in all other respects the chemistry matches that for the rock containing kryptonite. We will have to be careful with it - we wouldn't want to deprive Earth of its most famous superhero!"

The Krytonite will be revealed to the public in free events at the Natural History Museum on Wednesday 25 April and Sunday 13 May. Clark Kent need not attend.