foundameteorite - Museum of Natural Sciences

Meteorites are complex. It takes quite a bit of experience to identify them. Visit the Museum of Natural Sciences to see examples of meteorites and get an idea of the range of "looks" meteorites have. If you think you might have one, take it to the main office of the Geological Sciences department for analysis. But there are some clues you can look for first.

Shape

Most meteorities are the result of fragmentation in the atmosphere. They range from angular to boxy with melt-rounded corners and edges. Irons tend to be more rounded-looking than stones. Other shapes are possible including highly irregular, spindly, flattish, or shard-shaped like shrapnel. Rare button-like or bullet-like shapes can be produced when oriented fragments melt just on one side or end. Specimens from old falls may have undergone extensive weathering while on Earth, and their original shapes may have been modified.

Weight

Most meteorites contain at least a little metallic iron and so they range from just noticeably more dense than the average field stone to about three times as dense. A few, however, are noticeably lighter than the average field stone.

Magnetism

About 90% of all meteorites will attract a common hand magnet and many attract even a fridge magnet. However, they themselves will not act as magnets. About 5% will not attract even a strong magnet.

Fusion crust

If fragmentation occurred while the incoming meteorite was still in light-flight (when it is glowing), the fragment surfaces will be coated with a thin layer of frozen melt, often less than a millimeter thick. This is called a fusion crust, and it is almost always originally black to dark brown regardless of the type of meteorite. Such crusts rust easily and take on a brownish to reddish brown colour often within a few years. Fusion crusts also often shrink as they cool during dark-flight and may develop contraction cracks, giving the surface an alligator-skin appearance.

Colour

Most stony meteorites are light to medium grey under the fusion crust when they first land, but become rusty after spending enough time on Earth, depending on the climate. But the fresh colour can vary from light grey to white, to dark grey or black, and even reddish brown. At the Museum of Natural Sciences, check out the NWA 869 specimen for an impact breccias with fragments of different colours.

Thumbprints

Irregular melting of the surface of a meteorite fragment while still in light-flight often causes the production of numerous small and usually shallow pits, the kind that can be formed by pressing one's thumb repeatedly into stuff mud.The proper name for such features is regmaglypts. They tend to be more pronounced in iron meteorites than in stone. At the Museum of Natural Sciences, check out the Sikhote-Alin specimen for small and well-developed regmaglypts, the Campo Del Cielo specimen for large and shallow regmaglytps, and the Jiddat Al Harasis 091 and Tenham specimens for poorly formed examples.