Via GeekPress, an amazing discovery:

Scientists unearth Superman's "kryptonite"

LONDON (Reuters) - Kryptonite, which robbed Superman of his powers, is no longer the stuff of comic books and films.

A mineral found by geologists in Serbia shares virtually the same chemical composition as the fictional kryptonite from outer space, used by the superhero's nemesis Lex Luther to weaken him in the film "Superman Returns."

"I 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," he said.

The article goes on to say that the substance is white in color. When talking about kryptonite, people generally think of the green stuff. But it actually comes in a variety of colors and types. Wikipedia tells us the following about white kryptonite:

Kills all plant life, whether Kryptonian or not. Induces decay immediately upon exposure, with a range of about 25 yards. The most prominent use of this variety in the comics was to destroy Virus X, which was revealed in a storyline in 1968's Action Comics #362-366 to actually be a form of plant life.

Well, that sounds pretty bad. Not quite as bad as I feared, though. Come to think of it -- with summer coming -- if I had some of that white kryptonite, I bet I could save plenty on this stuff...