It was found in the dry bed of river Hekandue, a left tributary of river Jasačnaja in the Magadan district, Russia.

The main mass of 272.3 kg was found in June 1967 by the geologist F. A. Mednikov during a survey. The mass was a triangual shaped thumbprinted meteorite lying among the stones of the brook bed. A second specimen of 51 kg was found in October 1967 at a distance of 20 m from the first one by I. H. Markov with a mine detector 1967. The main mass was turned in to the Academy of Sciences of the USSR.

During a new expedition in 2004, Dmitri Kachalin recovered about 50 kg of new material. Remarkably, many of the new specimens (about 20%)^[2] were found to contain olivine crystals and so revealed the silicated nature of the meteorite. The pallasitic structure was not discovered previously during studies on small metal-only sections of the original mass.

Composition and classification

Seymchan belongs to Main Group pallasites, but it is considered anomalous due to its high Ir content^[3]. Before the discover of its pallasitic structure it had been classified as IIE anmalous coarse octahedrite. Seymchan is considered a stable and rust-resistant pallasite.