Celebrating Meteorites in May!

Various meteorites in The Charleston Museum collection. The sliced section shows the metallic minerals within.

Meteorites come in various forms, but the three main categories are stony, iron, and stony-iron. The stony meteorites are very difficult to distinguish from standard Earth rock to the untrained eye. Typically, when a collector believes they have found a meteorite, they usually cite characteristics of an iron meteorite. This type tends to be very dense and heavy, magnetic, may have a metallic or rusty sheen, with possible features on the outside that look as if the metal has partially melted.

The odds of a meteorite making it to Earth’s surface alone is remote. Most meteors burn up in the atmosphere in the form of “shooting stars,” or are so small, once they reach the surface they are indistinguishable as anything significant. These tiny meteorites tend to hit the Earth with so much force they are instantly buried after impact, which means most meteorite-like objects collector’s find are more than likely just imposters. In fact, there are several materials present in the Lowcountry that can often be mistaken for meteorites because they bear a superficial resemblance. These imposters are often referred to by collectors as “meteor-wrongs” that are often thought to be meteorites based on the presence of holes or the fact that the rock is magnetic. However, since those characteristics aren’t unique to meteorites, it can lead to standard terrestrial stones being misidentified as extraterrestrial.

Metallic meteorites often are rusty due to exposure to water.

The most common “meteor-wrong” found in the Lowcountry is the mineral ore phosphate. Phosphate nodules often look like the conceptualized idea of a meteorite. They can be large, black, and covered with holes. Some of the larger pieces can also be quite heavy. However, there are several easy ways to tell if the sample is actually phosphate rather than a meteorite.

One quick test that can be performed on suspected meteorites is the “magnet test,”  which is conducted by simply placing a magnet on the sample to see if it sticks. If it does, most likely you have a meteorite. However, be aware that phosphate nodules can also be weakly magnetic, which can lead to a false positive using this method.

Phosphate nodules like this can get mistaken for meteorites by people unfamiliar with them

Phosphate nodules aren’t the only objects found in the area that are often confused for meteorites. Slag, which is waste from metal refinement, as well as discarded iron, can also be confused for meteorites. Both can be magnetic, more so than phosphate, and can also have holes that make them convincing “meteor-wrongs.” However, the holes in these are often produced either by tools or air bubbles that escape the metal as it cools. Like phosphate, these holes are not in the right orientation and can easily be used to eliminate them as potential meteorites. It simply requires a trained eye to tell the difference.

In the end, most rocks and objects found to be suspected meteorites are instead something more mundane. If someone thinks they have found a meteorite, the home tests can help eliminate some objects. However, as we’ve discussed, those tests aren’t full proof. To truly determine if a sample is of cosmic origin, seek out the advice of a professional.

Matthew Gibson
Curator of Natural History