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How to identify a meteorite

Meteorites are extremely rare. People can spend lives searching for them and find nothing. In a 99,9% of cases, people find in reality volcanic rocks, hematite, slag, but not meteorites. A meteorite is distinguishable from other terrestrial rocks in many aspects. Official analysis are made in just a handful of institutions around the world. Nevertheless, there are a few indicators that many people can check to discard something as a meteorite or continue with more analysis. How can you identify a meteorite?

Iron content

Most meteorites have iron. Only a small percentage do not. When people hold a meteorite for their first time they are impressed by the unexpectedly heavy weight. The iron content implies that meteorites are attracted to magnets. This is usually a field test to see whether something can be a meteorite.

Fusion crust

The outer layer of the descending rock melts due to the heat caused by friction. When it cools down, specially in stony meteorites there remain a layer of dark color called fusion crust. Because rock transmits heat poorly, the inner part of the meteorite stays cold even when the exterior was melting. Fusion crust is a really thin layer (1mm or less).

How to identify a Meteorite.

Fusion crust in a stony meteorite

Flow lines

Sometimes fusion crust has a feature called flow lines. These lines result from the molten material being moved by the air like tiny lava rivers that solidify once the temperature goes down. It is typical in stony and iron meteorites.

How to identify a Meteorite.

Flow lines in a stony metorite

Regmaglypts

Meteorites often acquire shallow soft pits on the surface that resemble a thumbprint. These marks are called regmaglypts and are due to ablation. They typically appear in iron meteorites although stony meteorites can display them too.

How to identify a Meteorite.

Regmaglypts in an iron meteorite

Inside a stony meteorite

In most stony meteorites (the ones that look like rocks) you can see chondrules and metal inclusions when they are cut. Chondrules are sphere-shaped tiny rocks. Metal inclusions are really common in stony meteorites and really uncommon in terrestrial rocks.

Chondrules in a stony meteorite slice

Inside an iron meteorite

If you happen to be able to cut an iron meteorite, which are extremely hard, and you bath it in nitric acid to etch it, you get amazing intricate lines that cannot form in an environment subjected to gravity. Besides, when cutting or polishing an iron meteorite, the leftover dust is gray whereas in high-iron terrestrial rocks this dust is reddish. In addition, most meteorites get a positive in a nickel test in contrast to most terrestrial rocks. You can get a nickel test online or in a pharmacy.

How to identify a Meteorite.

Pattern in an iron meteorite slice

In short, if you think that you found a meteorite, be aware that the chances for it to be a real meteorite are close to zero. Make sure it is attracted to a magnet first. If it is magnetic, most likely it is slag or hematite. Check if there is fusion crust, chondrules, flow lines, regmaglypts, etc. If there is and you want to make a bit surer, test the piece for nickel. If it is magnetic, it has flight markers like fusion crust and tests positive for nickel, you probably got a meteorite.

Click on the link to learn about meteorites: information about meteorites
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