Seymchan is a Stony-iron coarse octahedrite pallasite meteorite found in the dry bed of the river Hekandue, a left tributary of river Jasačnaja in the Magadan district, Russia, near the settlement of Seymchan. It was discovered in June 1967.
The main mass of 272.3 kilograms (600 lb) was found during a survey in June 1967 by geologist F. A. Mednikov. The mass was a triangular-shaped thumbprinted meteorite lying among the stones of the brook bed. A second specimen of 51 kilograms (112 lb) was found with a mine detector at a distance of 20 m from the first in October 1967 by I. H. Markov.
Seymchan belongs to Main Group pallasites, but it is considered anomalous due to its high Iridium content. Before the discovery of its pallasitic structure it had been classified as IIE anomalous coarse octahedrite. Seymchan is considered a stable and rust-resistant pallasite. The more interesting examples of of this meteorite contain olivine crystals as well as the Widmanstatten pattern which is crystal lattice pattern present in most iron meteorites.