Anomalous meteorite
An anomalous meteorite mostly fits a known group but differs from it in some important way.
An anomalous meteorite resembles a known group closely enough to be linked with it, but has one or more features that fall outside the group's normal range. Such meteorites are labelled with the group name followed by '-an', for example IAB-an, CM-an or eucrite-an.
The difference might be in oxygen isotopes, trace element chemistry, mineral composition or texture. Some anomalous meteorites are simply unusual members of their group, perhaps from an unusual part of the parent body. Others may come from a different but related parent body, and might one day be reclassified as members of a new grouplet.
Anomalous and ungrouped meteorites are especially interesting to scientists, because they extend the known range of Solar System materials. The meteorite Bunburra Rockhole, a eucrite-like stone with unusual oxygen isotopes that fell in Australia in 2007, is an example of a meteorite that challenged the idea that all eucrites come from Vesta.
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