How to Tell If the Rock You Found Is a Meteorite
Have you found a weird looking rock when out hiking and thought, “I bet that came from outer space!” I have. Sadly, it’s almost definitely not a meteorite. As cool (and lucrative) as it would be to chance on the remainder of a meteor that survived its trip through the atmosphere to strike Earth, finding a bonafide space-rock is lottery-winning lucky. People thinking they’ve found a meteorite is as common as socks, though. Still, it can’t hurt to check, so here’s a down-and-dirty guide to whether that cool looking chunk came from space or is just a dumb, boring Earth rock.
Meteorites are rare
Research conducted at the University of Manchester and Imperial College suggest around 17,000 meteorites weighing between 50 grams and 10 kilos strike Earth each year, which might sound like a lot, but we’re talking about tiny objects randomly scattered across the whole planet. Most of them fall into the oceans, and most of the ones that do hit land are small and unassuming, so the chance of you running into a meteorite randomly and actually noticing it are slim—only about 1,800 meteorites have been found in the United States in the past two centuries. You’d do better looking for diamonds, gold, and emeralds, all of which are more abundant than meteorites.
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The best spots for hunting meteorites
Despite their rarity, people still find meteorites occasionally—but usually they’re looking in the right places. The best spot to hunt for space debris is Antartica. Meteorites don’t fall there fall there more often than other places, but the dark chunks of rocks and metal are more noticeable against the white ground. Other spots meteorite hunters might consider are California’s Mojave desert and Africa’s Sahara. Think dark chunks against a light background.
How to tell if you’ve found a meteorite
If you manage to spot an out-of-place looking rock on a desert hike, don’t get too excited. It’s still probably not a meteorite. Here are some characteristics of meteorites and meteor-wrongs to help you identify whether you’ve gotten extremely lucky.
Actual meteorites tend to have these characteristics:
Fusion crust: Meteorites are usually coated in an ashy black layer of fused rock caused by the intense heat generated when they pass through the atmosphere. Although the color can changed to a rusty brown after years on Earth, the lack of something that looks like a fusion crust almost always means it’s not a meteor.
Density: Meterorites are heavier than other rocks their size. Iron meteorites are 3.5 times as heavy as a typical Earth rock. Stony meteorites are about one and half times as heavy. But a chunk of slag, a byproduct of industry, is heavy as well, and way more common than a meteorite.
Regmaglypts: Meteorites generally have smooth surfaces, but they are often covered in regmaglypts, small depressions that look like someone has pressed their thumbs into wet clay.
Magnetism: Most meteorites contain iron-nickel and will attract a magnet. Many Earthly rocks do too, though. Magnetite and hematite are common, heavier than other rocks, magnetic, and and can look like meteorites, so it’s not an easy process.
Non-streaking: If you rub most ordinary rocks against the unglazed side of a piece of kitchen or bathroom tile, it will leave a streak. Meteorites generally do not.
If your rock has any of these characteristics, it’s probably not a meteor:
Roundness: Meteors are almost never round. They are irregular shaped, as Earthly forces like erosion haven’t touched them.
Bubbles or holes: Terrestrial rocks often have bubbles or holes in them. Meteorites do not.
Radioactive or hot: Meterorites are almost always cool when they hit Earth. They don’t start fires on the ground. The trip through the atmosphere is quick and doesn’t heat up the inside of the rock. They are also not radioactive, so your Geiger counter is of no use.
So now do I have a meteorite?
If your rock has passed all these tests, it might be a meteorite—but it probably isn’t. Many Earth things can resemble meteorites. Slag is probably the most common meteor-wrong, but there’s also basalt, iron ore, coal, chunks of asphalt, charcoal briquets, etc. Basically anything could be (and probably has been) mistaken for a meteorite by someone.
It’s hard to get a professional to care about your little rock
As difficult as it to find a meteor, it might be harder to find a geologist who will help you identify it, so don’t take it down to the local university and knock on the door of the geology department. Geologists have had it with people coming in asking about the weird rock they found. Check out this awesomely crotchety rant from lunar geochemist Randy L. Korotev from Washington University in St. Louis that begins: “In 2022, I was contacted 5,905 times by 2,095 different persons from 89 countries…Nearly all of these people questioned whether they had found, bought, or inherited a meteorite,” and ends with, “Other scientists who study meteorites have had the same experience and most no longer respond to questions from the public.”
If you give people money though, they will be happy to tell you haven’t found a meteor. Prices vary from lab to lab, but it’s not incredibly expensive: New England Meteoritical Services, for instance, will test a small sample of your rock for only $30. (I have no idea if they’re reputable, and I’m not recommending them—just giving you an idea of the price.)
The other option is to just tell everyone you found a meteor. Unless you’re friends with geologists, who’s going to know?
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