IOWA CITY— Ray Anderson has seen thousands of strange-looking rocks famers suspected could be meteorites.
Only one was. The rest he calls “meteor-wrongs.”
“They’re not really uncommon, if you think about cosmic dust — about a shoebox of that falls per acre every year on earth,” explained Anderson, a retired professor of geophysics with the University of Iowa and Iowa Geological and Water Survey.
Bigger meteorites are much rarer — and finding them almost impossible — but Anderson said farmers have a sharp eye for unusual objects in their fields.
“They’re the guys that are used to looking at the soil and the land, they’re used to looking at rocks, and they know when they see something unusual,” he said.
Meteorites are especially hard to find in the Midwest, where glaciers pushed a variety of strange-looking rocks.
“In Iowa, we’re blessed with all this wonderful glacial soil, and the glaciers basically took a sampling of every rock that exists between where you’re at and central Canada,” Anderson said.
Farmers have made several famous meteorite discoveries in Iowa history, though.
“(In the 1930s) around the town of Mapleton, a farmer was plowing his ground . . . all the sudden, here’s a big rock in the middle of his field,” Anderson said.
“He thought, ‘This is pretty unusual.’ ”
As the story goes, the farmer tossed it in a corner of the barn and went home, opened his mail and found a National Geographic Magazine with a story on meteorites.
He compared the photo in the magazine with the rock in his barn and realized he had something special.
In Lone Tree in 1972, a farmer found another meteorite while plowing.
“He’s in an area along the river there where he’s dealing with sand and silt and all of the sudden here’s a big rock which doesn’t belong there. So, how did it get there?” Anderson said.
“He figured out it might be something weird, and he hauled it up to the University of Iowa and the professors here identified it as a meteorite.”
There are a few characteristics that can separate meteorites from Earth’s lookalikes, such as the sample of iron ore Anderson keeps in his collection from the Mesabi Range in Minnesota.
“First thing you want to look for is, is it magnetic? And, not everything that’s magnetic is a meteorite, and not all meteorites are magnetic,” he said.
The identification process can be confusing.
“If you have a rock that’s real heavy and a magnet sticks to it, that’s a good clue. That doesn’t prove it — like I said, I’ve had a lot of those, and none have been meteorites.”
Other characteristics include a solid, dimpled surface or a fusion crust on the outer edges — a crust that forms when the rock burns through the atmosphere. It should have no holes (that can indicate lava), no layers and no quartz mineral presence.
“If I find one quartz crystal in here — and that’s about all you might find in something like this — you can say, ‘aha!’ ” Anderson said, holding up an example of one of the “meteor-wrongs.”
Washington University Professor Randy Korotev offers a self-test checklist online and a list of about 50 sometimes humorous reasons the rock you found isn’t a meteorite at http://meteorites.wustl.edu/realities.htm. The list covers colors, shapes, locations and probability.
Seven meteorites have been found and validated in Iowa and 23 in Missouri, according to the Meteoritical Society data base.
Numbers get much higher in the U.S. Southwest desert, where the terrain makes them much easier to find.
“During 2012, I was contacted 2,277 times by 907 different people from at least 64 countries who thought that they had found, bought or inherited a meteorite,” Korotev wrote. None were meteorites.
“But, a lot of meteorites in the U.S. were found by farmers!” he added.Though these rocks aren’t likely to be visitors from space, Anderson said they still have stories.
“If you’ve got something unusual, bring it in. Heck, we’d like to see it!” he said.
“Every one of these rocks have a story, and when you’re a geologist as long as I’ve been, I can pick up a rock like this ugly old rock and talk about it for an hour. I usually try to tell them how cool their rock is.”
Contact the Iowa Geological and Water Survey at 319-335-1575.