If Superman is out there somewhere, then he might get a fright - because so is his nemesis kryptonite, according to scientists.
Researchers have made a "once in a lifetime" discovery. A real life substance which matches the unique chemistry of kryptonite - as listed in the movie Superman Returns - does exist.
But if the superhero is protecting us all, then he needn't worry because the real version is white, powdery and unradioactive, compared to the fictitious radioactive green crystals that devastate his strength.
And while the mysterious green rocks come from outer space, the real mineral was found in Serbia.
Geologists from mining group Rio Tinto enlisted the help of mineralogist Dr Chris Stanley from the Natural History Museum after finding the unusual mineral.
After performing detailed tests on the substance, in a routine web search Dr Stanley was astounded to find its chemical formula exactly matched the kryptonite in Superman Returns.
The formula of the new discovery - sodium lithium boron silicate hydroxide - is the same as a scientific name written on a case of rock containing kryptonite stolen by Lex Luther in Superman Returns.
Dr Stanley described his amazement. He said: "I was flabbergasted. It is exactly the same as the formula from the film other than that one contains some fluorine.
"To find a mineral that matches the formula from fiction so closely really is a once in a lifetime coincidence.
"I nearly fell off my chair and straight away sent emails to all my colleagues who I'd worked with on this, telling them about it. It was one of those moments where you just think 'wow'.
"It is a case of truth being stranger than fiction in some ways. I don't know of previous discoveries of minerals in nature that have previously been predicted in this way by science fiction."
But he added that the real-life substance was completely harmless, saying: "It's difficult to interpret what is meant by Kryptonite in the movies.
"But I suspect that the chemical name on the case that Lex Luther steals might actually contain the kryptonite, which contains Plutonium, a very radioactive substance.
"So there's no way that if he is out there, Superman will be harmed by this substance!"
Dr Stanley said cracking the chemical code of the new mineral was a complex process.
He said: "It was first found by Rio Tinto and they called me in to try to find out what it was.
"But I needed to bring in an expert Canadian team to find out the mineral structure because the grains were particularly small and too small for normal techniques.
"Once they had worked out the structure, myself and the team at the Natural History Museum determined the chemistry.
"Then we made the application to have it registered and named as a new mineral by the International Mineralogical Association.
"It was then that I made the discovery when doing a routine Google search."
The new mineral will be unveiled at the Natural History Museum on Wednesday, named Jadarite after the Serbian region Jadar where it was found.
Dr Stanley said: "Like most minerals, it's named after where it was found. But I think it will always be remembered for the Superman connection."
He added that the mineral could prove a useful source for lithium to make batteries, as well as boron silicate to make heat resistant glass Pyrex.
He said: "It could definitely be a useful resource. And as far as new minerals go, where it was found it is really very abundant. And we would expect it to be easily found in other places."
On how he expected Superman enthusiasts to react to the news, Dr Stanley quipped: "They might be pleased, but then they might not - they are a law unto themselves."
Approximately 30 to 40 new minerals are discovered each year, but they are rigorously examined to check they are actually new before being recognised by the International Mineralogical Association
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