How to Identify a Meteorite (and Rule Out a Meteorwrong)

Knowing the common fakes first saves you time, because you can spot most of them in seconds.

Slag is the waste left over from smelting metal. It is dark, heavy, often magnetic, and it turns up anywhere people have burned coal or worked iron — old rail lines, factory sites, farm fields, riverbanks. It is the single most common meteorwrong. The giveaway is bubbles, and we come back to that below.

Magnetite and hematite are iron minerals that occur naturally all over the world. They are dense, dark, and magnetite is strongly magnetic. Rounded ironstone nodules and hematite concretions fool almost everyone, because they are heavy, dark and oddly shaped — exactly what people expect a space rock to look like.

Iron ore and rusted scrap round out the list. Old machine parts, ploughshares, grinding balls and mine waste all weather into shapeless brown lumps that feel far too heavy to be ordinary stone.

Nearly every meteorite contains metallic iron, so nearly every meteorite pulls on a magnet. That makes the magnet the fastest first check, and also the most over-trusted one.

The problem is simple. Magnetite, most slag and much iron ore all stick to a magnet too. So a rock that sticks has passed a test that almost every meteorwrong also passes. It tells you very little on its own.

What the magnet is genuinely good for is ruling things out. If a magnet shows no pull at all, your rock is very unlikely to be a meteorite. A small number of rare types hold almost no metal, but they are unusual enough that a completely non-magnetic find is nearly always terrestrial.

One practical note. Use a modest magnet, hung on a piece of string so you can feel the tug. Avoid rubbing a powerful rare-earth magnet all over the surface. If the rock does turn out to be real, that magnetic scrubbing wipes out the natural magnetism locked inside it, which is information scientists want and cannot get back.

A meteorite enters the atmosphere fast enough that its outer skin melts. That molten skin chills in seconds into a thin dark rind called fusion crust, and on a rock that fell recently it is the most convincing single feature you can see.

Real fusion crust is thin — typically under a millimetre — and it is matte, not glossy. Think of the dull black of a charcoal briquette rather than the shine of glass or glaze. It often shows fine flow lines, faint ripples running in one direction, made by melted material streaming backwards during the fall. Sometimes it also shows tiny contraction cracks, like the crazing on old pottery.

The crust also creates a striking contrast. Break or chip the edge of a fresh stony meteorite and the inside is usually pale grey, so you get a dark shell around a light interior. That contrast is a strong signal.

The catch is weather. Fusion crust does not survive long on the ground. Rain, frost and soil chemistry strip it away over years, and the surface rusts to a dull brown instead. So an old find can be a genuine meteorite with no crust left at all. Present crust counts strongly in favour; absent crust proves nothing either way.

During the fall, hot gas scours the surface unevenly and leaves shallow dents in the skin. They look uncannily like the marks left by pressing your thumb into soft clay, and geologists call them regmaglypts.

The look is specific and worth learning. They are shallow, smooth-bottomed and rounded, roughly the size of a fingertip, and they run into one another across the surface. They are dents, not holes.

That distinction does the work. Slag has holes — round gas cavities that go into the rock and often break through. Weathered ironstone has smooth curves but not the scooped, overlapping pattern. Deep pits, sharp-edged cavities and holes that pass right through are all signs of something terrestrial.

Pick the rock up and compare it with an ordinary stone of the same size. Meteorites are notably heavier. Iron meteorites are dramatically so — an iron the size of a tennis ball feels like a joke, because metallic iron is roughly seven to eight times the weight of the same volume of water, while a common rock is closer to three times.

Stony meteorites are subtler. They are denser than most ordinary rock, but not by a margin that always announces itself. Handled next to a similar-sized piece of granite or limestone, a stony meteorite feels a bit heavy for its size, not shockingly so.

The reason this matters is that it works in both directions. A rock that feels light for its size is almost certainly not a meteorite. But heft alone never confirms one, because magnetite, hematite and slag are all heavy too — that is precisely why they get mistaken for meteorites in the first place.

This is the test that eliminates the most meteorwrongs, and it costs nothing. Take a piece of unglazed porcelain — the rough underside of a bathroom tile or a ceramic mug works — and drag the rock across it firmly. Look at the line of powder left behind.

A meteorite leaves little or no streak. At most you get a faint grey mark, because the metal in it does not powder easily against ceramic.

A meteorwrong usually leaves an obvious one. Hematite streaks reddish-brown, every time, regardless of what colour the lump looks on the outside. Magnetite streaks black. Those two minerals account for a large share of all mistaken finds, so a strong reddish-brown or black streak is close to a verdict on its own.

Our **streak test guide** covers the technique and the colour chart in more detail, including why the powder colour is often nothing like the colour of the rock.

If your rock is still standing after the first five tests, this is the one that usually settles it.

Using a file or a bench grinder, cut a small flat patch through the weathered outer surface — a window about the size of a fingernail is plenty. Keep it small and put it on the least attractive face. You want to see fresh material, not destroy the specimen.

In a stony meteorite you will usually see bright metal flecks scattered through a grey background, like tiny specks of clean steel. Those flecks are metallic iron, and they are the point of the whole exercise, because free metal grains simply do not occur in ordinary Earth rocks. You may also see chondrules, small round grains about the size of a pinhead, which we come back to below.

In an iron meteorite the window shows solid bright metal, not a mixture at all.

A meteorwrong looks nothing like this. Slag is glassy or frothy inside. Magnetite is dark and uniform. Hematite is red-brown under the skin. Ordinary rock shows interlocking crystals or grains, sometimes layers, but never scattered specks of shiny metal.

Some features are not evidence against a meteorite so much as proof of something else. If you see any of these, you can stop testing.

This is where home testing runs out, and it is worth understanding why.

The metal in a meteorite is not plain iron. It is an iron-nickel alloy, and the nickel content is the closest thing identification has to a fingerprint. Natural metallic iron on Earth is genuinely rare, and the ordinary iron in ore and rusted scrap does not carry nickel in the same way. So metal plus nickel is a combination that is very hard for a terrestrial rock to fake.

There is a caveat, and it is the reason nickel is a strong clue rather than a proof by itself. Some manufactured steels are alloyed with nickel deliberately. A rusted stainless fitting can pass a crude nickel check while being entirely man-made.

You can buy nickel spot-test chemicals, but reading them correctly takes practice and a fresh, clean metal surface. Getting a false answer is easy. The reliable confirmation is a laboratory measuring the actual composition of the metal. A lab can also cut and etch an iron sample to look for the Widmanstätten pattern — a criss-cross lattice of interlocking metal bands that forms only when molten metal cools over millions of years. Nothing made in a furnace has ever had that long to cool, which is why the pattern is treated as decisive.

Run these in order. Each row tells you what the test genuinely settles, which is often less than people assume.

Knowing which type you might be holding changes what you should expect to see.

If your cut window shows chondrules, you are almost certainly holding a meteorite.

Chondrules are tiny round beads of silicate, roughly a millimetre across, and they formed as free-floating molten droplets in the early solar system before anything resembling a planet existed. They cooled in open space and were later swept up into the rocky bodies that became asteroids. That history is the important part: they are older than the Earth, and there is no process at work on our planet that makes them.

So while a magnet, a heavy feel and a dark crust are all suggestive, visible chondrules are something different in kind. They are a feature the Earth cannot produce. Look for them as faint round outlines on a cut and lightly polished surface, sometimes standing out because they weather at a different rate from the material around them.

First, protect the specimen, because how you handle it affects both its scientific value and how easy it is to identify.

Do not clean it with acid, do not polish it, and do not heat it. Keep it dry, since the iron inside will rust and once rust takes hold it spreads through the specimen. Handle it as little as you can. Write down exactly where you found it, ideally with a GPS reading, along with the date and anything you noticed about how it was sitting. Provenance is not paperwork — a meteorite with no known find location loses much of what makes it useful.

Then get a real opinion. University geology and earth science departments with meteorite research groups are the usual route, and several well-known ones accept identification requests from the public. Large natural history museums often do the same. Local geology clubs and university extension offices can point you to whoever is nearest.

Approach them the sensible way. Send clear photographs first, including one of a cut or filed window and one with a ruler or coin for scale, plus your test results and find location. Terms vary between institutions — some ask for a fragment, some charge for detailed analysis, some only look at strong candidates — so ask what they need before posting anything. Never send your only specimen without agreeing first how it comes back.

And if you want a quick first read on a rock before you go to that trouble, our **rock identifier** gives you an instant answer from a photo, with an honest confidence score attached.

Ownership rules differ from country to country, and sometimes within a country, so treat this as a prompt to check rather than an answer.

The broad pattern in many places is that a meteorite found on private land belongs to the landowner rather than the finder, which makes asking permission before you search the practical and honest move. Public land is usually more restricted, and rules vary sharply between different kinds of protected and managed land.

Some countries go further and treat meteorites as national heritage, restricting export or requiring that finds be reported or offered to a national collection. Others have little specific law at all.

The safe approach is the same everywhere. Find out who owns the ground before you look, get permission in writing when you can, and check your own country's rules on reporting and export before you sell, ship or take anything abroad.

Two natural glasses come up constantly in meteorite questions, and both are worth separating out.

**Tektites are genuinely connected to an impact, but they are not meteorites. When a large body strikes the Earth, the collision melts surface rock and throws molten droplets into the air, and those droplets chill into glass. So a tektite is melted Earth, not the visiting object. They are dark, glassy, light in the hand and essentially non-magnetic — the opposite of an iron meteorite in every measurable way. Moldavite**, the green gem variety, is the most famous example.

**Obsidian** is volcanic glass. It has no space connection at all, is light for its size, and breaks with the sharp curved surfaces typical of glass. It is regularly mistaken for a meteorite because it is black and shiny, but shine itself is a warning sign: fusion crust is matte.

If you are working through look-alikes in general, our **guide to identifying rocks covers the standard diagnostic tests, the Mohs hardness scale explains the scratch test that separates many similar-looking minerals, and how to tell if a crystal is real** covers the same sceptical approach applied to gems and crystals.