How to Tell if a Rock is a Meteorite (Real Tests That Work)

Fusion crust is the single strongest positive indicator of a meteorite. When a meteoroid enters the atmosphere, its outer surface melts and then rapidly solidifies as the object decelerates, forming a thin glassy coating typically 0.5 to 2 millimeters thick. This coating is almost always dark brown to black on fresh falls, with a smooth to matte surface texture that may show subtle flow lines oriented in the direction of flight.

No common terrestrial rock-forming process creates an equivalent coating. Volcanic rocks can have dark exteriors, but their texture is fundamentally different: vesicular, crystalline, or sedimentary rather than the smooth flow-banded character of fusion crust. If you find a rock with an intact dark glassy exterior that shows no bubbles, no crystal faces, and no sedimentary layering, fusion crust is a serious possibility worth investigating further.

Fusion crust weathers over time. Meteorites that have been on Earth for decades show increasingly degraded crust: brown rather than black, patchy, or almost absent. A lack of visible fusion crust does not rule out a meteorite, but its presence is a strong positive signal.

Most meteorites are attracted to a strong magnet. Iron meteorites are strongly ferromagnetic and will hold firmly to a neodymium magnet. Ordinary chondrites contain metallic iron grains dispersed through their silicate matrix and show a clear magnetic response. Use a strong neodymium magnet rather than a refrigerator magnet, which may be too weak to detect the response in metal-poor stony meteorites.

The limitation of this test is that many terrestrial rocks are also magnetic. Magnetite is strongly magnetic. Some basalts contain enough iron minerals to attract a magnet. Magnetism is a necessary but not sufficient condition. It narrows the field significantly, but a magnetic rock still needs to pass other tests.

One important exception: some achondrites, lunar meteorites, and Martian meteorites contain very little metallic iron and show minimal magnetic response. A rock that does not attract a magnet is not automatically ruled out, though it is less likely to be a common chondrite or iron.

Pick up your specimen and then pick up a terrestrial rock of similar size. If the specimen feels noticeably heavier, that is significant. Iron meteorites have densities of 7 to 8 g/cm³, roughly twice the density of granite. Stony meteorites average around 3 to 3.5 g/cm³, still denser than most common rocks.

You can measure density more precisely using water displacement: weigh the specimen on a scale, then measure the volume of water it displaces when submerged. Divide weight by volume to get density in g/cm³. A stony meteorite should come in around 3.0 to 3.5. An iron meteorite around 7 to 8. Common terrestrial rocks such as sandstone, granite, and limestone typically fall between 2.5 and 2.9.

This is the fastest elimination test available. Examine your specimen carefully on the surface and on any broken or cut faces. If you see rounded holes, elongated voids, or a bubbly interior texture, your specimen is almost certainly not a meteorite. These vesicles form when gases are trapped in cooling volcanic or industrial material. Meteorites essentially never have them.

This single test eliminates the vast majority of meteorite misidentifications. The most common false positive, industrial slag, almost always has vesicular texture. Vesicular basalt is another common misidentification that the bubble test immediately rules out.

Drag your specimen firmly across an unglazed ceramic tile. The color of the mark left behind is diagnostic for several common meteorite look-alikes. Hematite leaves a reddish-brown streak. Magnetite leaves a black streak. Meteorites leave either a very faint metallic gray streak or no visible streak at all.

If your magnetic, dense rock leaves a red or black streak, it is almost certainly a terrestrial iron oxide mineral rather than a meteorite. This one test resolves a large proportion of magnetite and hematite misidentifications.

Rules out the two most common magnetic look-alikes in seconds.

Regmaglypts are the shallow, rounded depressions sometimes described as thumbprint impressions that form on the surface of some meteorites during atmospheric flight. As the outer surface ablates in the high-temperature entry environment, flowing air creates pockets of lower pressure that erode the surface in a characteristic pattern. They are more common on iron meteorites and stony meteorites with high metal content.

Not all meteorites have regmaglypts and their absence does not rule a specimen out. But when present alongside other positive indicators, fusion crust, magnetism, and no bubbles, they are a strong supporting signal.