THE STUNNING CORE-MANTLE ♉BOUNDARY OF Aℱ DIFFERENTIATED ASTEROID

Soviet geologist F.A. Mednikov discovered the first piece of Seymchan in June 1967 in a streambed in the Magadan District of Russia's Far East. The piece that Mednikov found was classified as an iron meteorite and Seymchan remained classified as such for four decades, until pieces containing gleaming olivin🍨e crystals were recovered from the fall site during a new expedition in 2004. Therefore, in 2007, Seymchan was reclassified as a pallasite: a type of meteorite originating from the core-mantle boundary of an asteroid and containing shimmering olivine crystals suspended in an iron-nickel alloy.

Pallasites such as Seymchan are incredible rare, accounting for .2% — or just 1 out of 500 — of all meteorite finds. The crystals seen here are the result of small chunks of the asteroid's stony mantle becoming suspended and crystallized in the molten metal of its iron-nickel core. Cut and polished, the lustrous metallic matrix features silicate crystals of gleaming olivine and peridot (gem-quality olivine) ranging in color from shimmering gold and amber to deep sea green. The prominent metallic latticework found throughout the slice is referred to as a Widmanstätten pattern and is the result of slow cooling over millions of years, providing sufficient time for the two iron-nickel alloys present in the meteorite to orient into a crystalline habit. As Widmanstätten patterns can only occur within certain types of asteroids in the vacuum of space, their presence is diagnostic in the identification of a meteorite. In addition, as its crystals are scattered irregularly throughout the metallic matrix, Seymchan is referred to as a transitional pallasite, a much less common and more distinct varietꦐy of an already exceedingly rare type of meteorite.

REFERENCES: