Seymchan 33.6g

Seymchan is the meteorite that kept on getting more interesting as time went on. First discovered during the summer of 1967 by the Russian geologist F. A. Mednikov, it was originally classified as a IIE iron meteorite. In the early 2000s, meteorite hunters associated with the Vernadsky Institute in Moscow returned to the site in the hope of finding additional specimens. They did. And there were amazed to discover not iron meteorites, but pallasites — stony-iron meteorites encrusted with olivine crystals. Their finds resulted in a rare classification change in the scientific literature: in 2007 van Niekerk et al. revised the designation for Seymchan from iron to pallasite.

Seymchan has an unusual structure: some areas display olivine-rich clusters, while others (like this one) consist almost entirely of nickel-iron. During its tumultuous flight through the atmosphere and subsequent impact, it is easy to imagine the meteoritic masses of Seymchan shearing at the nickel-iron/olivine borders. Some pieces, therefore, appear to be entirely metallic, while others appear pallasitic. This explains why Mednikov found what he assumed to be an entirely iron, or sideritic meteorite, while later expeditions found what they assumed to be pallasites.