Seymchan Meteorite is a type of pallasite meteorite, a type of stony-iron meteorite that has yellow - green Olivine crystals embedded within. Unlike other Pallasite meteorites like the more common Sericho, Seymchan is unusual as the Olivine crystals are clustered in the outer crust, whereas the centre is a much more solid metal, this makes for particularly interesting larger specimen slices where a larger cross section can be seen. Only around 10 - 20% of Seymchan specimens contain olivine crystals.
The Seymchan meteorite was first discovered in 1967 in the dry riverbed of the Hekandue River in Magadan Oblast, in the far east of Russia. The nearest town was the small settlement of Seymchan, with a current population of around 2,800 people, after which it was named. There is no current record of when it fell to earth as the fall was unseen (although this would technically be possible to date with cosmogenic radionuclide dating, which Stu has explained to me at length, but I won’t bore you with the details!), but the original parent asteroid from which the Seymchan broke off from is believed to date back 4.5 billion years to the asteroid belt between Mars & Jupiter.
When it was first discovered, the Seymchan meteorite was thought to be a “normal” iron meteorite, as no pieces with olivine in were discovered at first (due to it’s uneven Olivine distribution), it wasn’t until the turn of the 21st century that specimens containing Olivine were discovered, and it was reclassified as a pallasite.
Unlike Sericho meteorite, Seymchan is much more resistant to rusting, this is due to the unusually high content of rare metal iridium, which is the most rust / oxidation resistant metal known on Earth.