Magnetic attraction

If you have a rock that does not attract a magnet, then almost certainly it is not a meteorite

Most meteorites will attract a cheap ceramic magnet

Meteorites are not “magnetic.” Meteorites are not magnets – they do not attract paper clips or pins. Most (>95%) meteorites (chondrites, iron meteorites), however, do attract a magnet because they contain a lot of iron-nickel metal.

If you have a rock that does not attract a magnet, then almost certainly it is not a meteorite. Some of the rarest kinds of meteorites (achondrites, lunar meteorites, martian meteorites), however, do not attract magnets because they contain little or no metal. Most terrestrial (Earth) rocks also do not attract magnets for the same reason.

If you have a rock that does attract a magnet, then it is also probably not a meteorite because the mineral magnetite is common in Earth rocks. Cut or break the rock open. If it has metal flecks or veins like in these ordinary chondrites, then it might be a meteorite, but more likely it is just industrial slag, which often contain metal blebs.

NO – Neodymium (rare-earth) magnets are *not* useful for determining if a rock or piece of metal is a meteorite. If it is shiny, do not use it. This rock is probably a mixture of the minerals hematite (reddish) and magnetite. Both are iron oxides, not metal. Magnetite attracts magnets.

Do not use a neodymium (rare-earth) magnet. Those things are so strong that they will attract many kinds of terrestrial rocks. An ordinary chondrite or iron meteorite will respond to an inexpensive ceramic or ferrite magnet. In the U.S. we often call these “refrigerator magnets.”

**YES – Use a cheap refrigerator magnet. These usually have a dark brown ferrite magnet stuck to the back.**

If you have a piece of metal that does not strongly attract a ceramic magnet, then it is definitely not a meteorite.

If you have a piece of metal that does attract a magnet and want to know if it is an iron meteorite, obtain a chemical analysis for the elements iron (Fe), cobalt (Co), nickel (Ni), chromium (Cr), and manganese (Mn). Iron meteorites will have 75-95% Fe, 5-25% Ni, 0.2- 2% Co, and <0.1 % (<1000 ppm) each Cr and Mn. A metallurgical lab can provide this analysis. In the right hands, a hand-held XRF analyzer can also be useful.

A good way to test if a rock is attracted to a magnet is with a circular ceramic magnet **(usually dark in color)**. Put it on its edge on a flat, hard surface. If a rock attracts a magnet, you can cause the magnet to roll by pulling the magnet with the rock.

**Iron meteorites strongly attract an inexpensive magnet.**

Magnetite (Fe₃O₄) is a common Earth mineral. It readily attracts a cheap ceramic magnet. Because this rock is reddish, it probably also contains hematite (Fe₂O₃). *Pure* hematite does not attract a magnet.

I will say it again: Do not use a neodymium (rare-earth) magnet. The rock above is not a meteorite, it is a rock from Earth that is rich in the mineral magnetite. It contains enough magnetite to attract rare-earth magnets, but not enough to tightly hold a cheap ceramic magnet. Magnetite-rich rocks without hematite are often gray to blackish. Note that the rock contains vesicles, which is another clue that it is not a meteorite.

“Magnetic absorption” measured by mobile phones

We want to know if the rock attracts a magnet. You cannot use a mobile phone to determine if a rock attracts a magnet. Use a magnet. I receive numerous emails with statements like, “It has 30% magnetic absorption.” I did not know what that meant at first. Then I learned that there are apps for mobile phones that measure “magnetic absorption” – mini magnetometers that measure magnetic field strength. But, as noted above, meteorites are not magnets so they have a negligibly small magnetic field. Throw away your mobile phone. They are useless for determining if a rock is a meteorite.

I have not tested this, but I suspect that iron meteorites and pieces of man-made iron-rich metal may have small magnetic fields, but again, you don’t need a mobile phone to determine if a piece of metal contains iron.

back to “Some Meteorite Realities”