If you remember from the comic books, the Man of Steel would use his superhuman grip to crush a piece of coal into a pure, glistening diamond.

Sounds wild, but that's really just a sped-up version of what geologists have long assumed is the way diamonds are made: the decaying remains of ancient carbon-based organisms were dragged down over time into the depths of the Earth, where high heat and pressure formed the carbon into diamonds. Coal, after all, is just decayed plant matter.

But in a paper published in the journal Science, Haggerty, a geoscientist at the University of Massachusetts, asserts that diamonds on Earth are just too old to have been formed from the remains of plants and marine life.

Diamonds found on the planet, he says, were formed at a time when there just wasn't enough organic material on Earth to yield a suitable amount of carbon for diamond production.

Instead, Haggerty says, tests have linked Earth-based diamonds to those found on meteorites, indicating that the carbon which served as an ingredient for diamonds came from early Earth impacts.

Those tests compared the ratio of two isotopes of carbon -- a heavy version (with 7 neutrons) and a light version (with 6 neutrons). The ratio can be seen as a signature, indicating whether different objects had similar origins.

The signature of Earth-based diamonds matches those on meteor-based diamonds, whereas the signature of decaying biological matter has a much different signature, with too high a prevalence of the lighter isotope. According to Haggerty, this strongly suggests a "stardust" theory for the origin of diamond formation.

"The logical conclusion is if one can eliminate the biologically-mediated carbon, then the next and obvious conclusion is that the carbon must be extraterrestrial," Haggerty said in an interview.

This theory has broader implications for the origins of other minerals found on Earth. Haggerty's research suggests that geoscientists need to pay more attention to cosmic sources when looking at the atomic ingredients of minerals.

All this is not to say that Superman would not be able to make diamonds from coal. Carbon from decaying biological matter would be just as good as meteor-based carbon in the production of diamonds. Life may not have been around long enough, however, for diamonds to be formed from this source.