Are Meteorites Magnetic?
Meteorite Identification
Most meteorites are magnetic, but a magnetic response by itself is not enough to identify a meteorite. The magnet test is best used as a first-pass screen: if a stone does not attract a magnet at all, it is almost certainly not a meteorite. If it does, it has earned further testing.
Why Most Meteorites Are Magnetic
The vast majority of meteorites contain iron-nickel metal, either as discrete grains within a stony matrix (chondrites) or as the dominant material of the specimen itself (iron meteorites). This metallic iron-nickel alloy is ferromagnetic, which means it responds firmly to a household magnet and very firmly to a strong neodymium magnet.
Iron-nickel metal is essentially absent from common terrestrial rocks. On Earth, native iron exists only in unusual settings such as certain basalts on Disko Island in Greenland or as trace inclusions in some volcanic rocks. The presence of significant metallic iron-nickel is therefore one of the most useful chemical markers of meteoritic origin, and the magnet test is the easiest way to detect it.
This makes the magnet test extraordinarily useful for screening suspect stones in the field. A meteorite hunter can sweep dozens of candidate rocks in a few seconds with a magnet on a stick, immediately rejecting the ones with no magnetic response. The technique is so effective that nearly every serious meteorite hunter carries a strong rare-earth magnet at all times.
Magnetic Response by Meteorite Type
How to Perform the Magnet Test
The standard field magnet test takes only a few seconds and requires nothing more than a strong magnet, ideally a neodymium (rare-earth) magnet that can be safely held against the stone without crushing fingers between magnet and rock.
Step 1: Bring the magnet near the stone
Hold the magnet a few millimeters from the surface and slowly move it closer. A meteorite will tug the magnet noticeably before they make contact. A non-magnetic rock will not.
Step 2: Try multiple spots
Some stony meteorites have unevenly distributed metal grains. Test several different points on the specimen rather than relying on a single contact.
Step 3: Compare to a known meteorite or to a piece of iron
The strongest response in a stony meteorite is generally weaker than the response of a pure piece of iron. Calibrating your sense of "magnetic enough" with a known reference helps avoid both false negatives (missing a true meteorite) and false positives (rejecting on too gentle a pull).
A magnetic response is necessary but not sufficient evidence of meteoritic origin. Many terrestrial meteor-wrongs (magnetite, hematite-magnetite intergrowths, slag, certain basalts, ferromanganese nodules) are also magnetic. Always combine the magnet test with other checks: surface features, streak test, density, and interior examination.
Why Some Meteorites Are Only Weakly Magnetic
Although most meteorites attract a magnet, several important categories are only weakly magnetic or essentially non-magnetic. Understanding which categories these are helps you avoid mistakenly rejecting a real meteorite simply because it failed an initial magnet test.
Lunar meteorites and Martian meteorites contain very little free metal. The Moon's crust formed by extensive magma ocean differentiation, and most of its iron sank into the lunar interior. Mars's surface is dominated by oxidized iron compounds (the famous Martian rust) rather than metallic iron. As a result, these planetary meteorites typically show only weak magnetic responses, or none at all to a normal magnet.
Carbonaceous chondrites also tend to be weakly magnetic. They are rich in carbon and water-bearing minerals but poor in free iron-nickel metal. Murchison and Tagish Lake are good examples of meteorites that pass virtually every other test for meteoritic origin but show only weak magnetic responses.
For these classes, expert analysis (oxygen isotope measurements, thin-section petrography, and chemical analysis) is essential. The magnet test alone could send a Martian meteorite to the rejected pile.
A meteorite that does not attract a magnet is extremely rare but not impossible. A "meteorite" that attracts a magnet but fails every other test is essentially always a piece of slag, magnetite, or another terrestrial mimic.
The Science: Why Iron-Nickel Is Magnetic
Iron-nickel metal in meteorites consists primarily of two alloys: kamacite (about 5-7% nickel) and taenite (25-50% nickel). Both are ferromagnetic at room temperature, meaning their atoms have aligned magnetic moments that produce a strong external magnetic field response.
This ferromagnetism is the same physical property that makes refrigerator magnets stick to steel appliances. In a meteorite, the metal grains often record the magnetic field that was present in the early solar system when they cooled and solidified, which is why paleomagnetic studies of meteorites are a major research area in modern planetary science. NASA and academic researchers use this information to study the early solar nebula's magnetic environment, with significant results published through outlets such as NASA Science.
Related Questions
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Frequently Asked Questions
Are meteorites magnetic?
Most meteorites are magnetic to some degree. Iron meteorites and stony-iron meteorites are strongly magnetic; ordinary chondrites are moderately magnetic; carbonaceous chondrites, lunar meteorites, and Martian meteorites are usually only weakly magnetic.
Can a fridge magnet identify a meteorite?
A standard fridge magnet can detect iron meteorites and most ordinary chondrites, but it may miss weakly magnetic specimens like carbonaceous chondrites or lunar meteorites. A strong neodymium magnet is more sensitive and more reliable.
If a magnet sticks to a rock, is it a meteorite?
Not necessarily. Many terrestrial materials are also magnetic, including magnetite, slag, certain basalts, and some hematite-magnetite intergrowths. A magnetic response is necessary evidence but not sufficient evidence of meteoritic origin. Combine it with other tests.
Can a meteorite be completely non-magnetic?
Yes, but it is rare. Most lunar meteorites and many Martian meteorites are only very weakly magnetic, and a few specialized achondrite classes show essentially no magnetic response. Expert identification is essential for these specimens.
Why is the magnet test the first test most experts use?
Because it is fast, requires no equipment beyond a magnet, and rules out the great majority of suspect rocks at a single touch. Combined with subsequent tests (streak test, interior inspection, density measurement), it forms the backbone of practical meteorite identification.
