Seymchan is a

pallasite The pallasites are a class of stony–iron meteorite. Structure and composition It consists of centimetre-sized olivine crystals of peridot quality in an iron-nickel matrix. Coarser metal areas develop Widmanstätten patterns upon etching. Mino ...

meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...

found in the dry bed of the river Hekandue, a left tributary of river Yasachnaya in the Magadan district,

Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...

, near the settlement of Seymchan, in June 1967.

History

The main mass of 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 was found with a

mine detector Demining or mine clearance is the process of removing land mines from an area. In military operations, the object is to rapidly clear a path through a minefield, and this is often done with devices such as mine plows and blast waves. By contra ...

at a distance of 20 m from the first in October 1967 by I. H. Markov. The main mass was turned over to the Academy of Sciences of the USSR. During a new expedition in 2004, Dmitri Kachalin recovered about of new material. Remarkably, about 20% of the new specimens were found to contain

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...

crystals, and so revealed the silicated nature of the meteorite. The pallasitic structure was not previously discovered 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

Iridium Iridium is a chemical element with the symbol Ir and atomic number 77. A very hard, brittle, silvery-white transition metal of the platinum group, it is considered the second-densest naturally occurring metal (after osmium) with a density of ...

content.van Niekerk, 2007 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.

Specimens

Due to the heterogeneous structure of Seymchan, there are two types of specimens: with or without olivine crystals. It is worthy to note that the specimen pictured to the left shows an interesting, seldom seen feature of iron meteorites. The

Widmanstätten pattern Widmanstätten patterns, also known as Thomson structures, are figures of long nickel–iron crystals, found in the octahedrite iron meteorites and some pallasites. They consist of a fine interleaving of kamacite and taenite bands or ribbons ...

on the left hand side of the specimen is visibly bent. This is caused by the shearing of the meteorite as it broke up during atmospheric entry and serves as testimony of the violent experience a meteor is subject to as it falls through the atmosphere.

References

External links

*
Meteoritical Bulletin Database
{{Meteorites by name Meteorites found in Russia Geography of Russia 1967 in the Soviet Union

History

Composition and classification

Specimens

See also

References

External links