Pieces of the moon and of Mars generally command higher prices than rocks from other planets.
A nice piece of Mars will run you, per gram, anywhere from $200 to $1,000. A moon rock typically commands $1,000 per gram or more. Twelker says he has a hard time selling anything priced over $30,000, though on his site right there's a "90-pound, beautiful, crusted iron meteorite" that fell to earth in Russia in 1947. Price: $39,000.
The most expensive meteorite of which he is aware is an 11 kilogram lunar chunk worth $11 million. Its owner, he says, is having trouble selling it. "You can't just dump something like that onto the market."
Could meteorites be considered an investment?
"For some people they could be," he says, "if you know what you're doing." Prices have gone up consistently since he started his website in 1995, he says. But an investor would have to know how to care for what he buys, given the fact that so many space rocks are subject to decay. "You've got to be good at managing the instability problem, or else you've got lumps of rust at the end of your investment period."
Then, too, transaction costs can erode profits. "The difference between what you pay and what you later can sell for is substantial," he says, "unless you manage to buy at dealer price and sell at retail." Certain collectors, he says, do quite well. "But I don't recommend it for the ordinary person."
What meteorite could be considered the most collectible one ever to visit Earth?
A case could be made for the rock whose impact is believed to have taken out the dinosaurs. Geophysicists think its impact site may have been what today is the Chicxulub crater, off the Yucatan Peninsula. Judging by that crater's size, the asteroid would have been some six miles in diameter.
If, however, a dealer ever tries to sell you a hunk of it (marketing slogan: "The Dinosaurs' Loss, Your Gain!"), walk away. You'd be better off saving up to buy the Brooklyn Bridge.
"Here again," explains Twelker, " the problem is one of instability. That asteroid hit the Earth 60 million years ago. It would long ago have disintegrated, or, as we say, terrestrialized."