Classification
Classification is the process of identifying exactly what kind of meteorite a specimen is and giving it an official type and group.
Once a rock is confirmed as a meteorite, scientists work out what kind it is. At the broadest level there are three main types: stony meteorites, mostly made of silicate minerals; iron meteorites, mostly iron-nickel metal; and stony-iron meteorites, a mixture. Stony meteorites are split into chondrites, which contain chondrules, and achondrites, which do not. Each of these is divided into groups thought to come from different parent bodies.
A full classification can look like a code. Chelyabinsk, which fell in Russia in 2013, is an LL5 chondrite: LL is its chemical group, and 5 is its petrologic type, showing how strongly it was heated inside its asteroid. Codes for shock stage and weathering grade are often added, such as S4 and W1.
To classify a meteorite, researchers study a thin slice under a microscope, measure the chemistry of minerals with an electron microprobe and, for some types, measure oxygen isotopes or trace elements. The result is submitted to the Meteoritical Society for approval. A classification cannot be done from appearance alone, so a seller's label should always be checked against the official records.
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Level: Explorer Ages 10 and up