Meteorite fusion crust, 4

A fusion crust is the most characteristic feature that distinguishes a meteorite from a plain old Earth rock. If a rock does not have a fusion crust and does not contain iron-nickel metal, then there is no reason to suspect that it is a meteorite, regardless of what other meteorite-like features it may have.

Two photos of the largest fragment of the Chelyabinsk (LL5 chondrite) meteorite recovered from Lake Chebarkul in central Russia, 8 months after it crashed through the ice on the lake on February 15, 2013. The fusion crust is still visible. The surface texture is more lumpier than for most meteorites because the meteorite was fragmenting throughout most of its passage through the atmosphere.

This meteorite, one of several stones (stone f, 5.4 kg) of the Seminole (H4-6) ordinary chondrite, was found in a cotton field in west Texas in 2008. The “smiley face” is a magnet. The fusion crust is weathered and has flaked off in a few places. Weathered fusion crusts are often reddish in temperate climates. The interior of the meteorite is largely unweathered, however (below). Photo credit: anonymous finder

Polished slice of Seminole (f), above, showing thousands of metal grains. There is no rust in the interior of the meteorite. Photo credit: Randy Korotev. Thanks to Phil Mani for the beautiful sample.

Two views of another meteorite found in a field in west Texas. From the find location, it is almost certainly another (yet unclassified) stone of the Plains [Plains and Plains(d)] H chondrite. As with Seminole (f) above, it has a rusty colored exterior from terrestrial weathering. The meteorite may have fallen hundreds or more years ago. Regmaglypts are still evident, however. Photo credit: anonymous finder

A fusion crust is the most characteristic feature that distinguishes a meteorite from a plain old Earth rock. If a rock does not have a fusion crust and does not contain iron-nickel metal, then there is no reason to suspect that it is a meteorite, regardless of what other meteorite-like features it may have.