Seymchan is an unusual and remarkable pallasite; large portions of the rock are olivine free. Pallasites are formed at the core-mantle boundary of an asteroid that experienced melting: molten metal from the core mixed with olivine crystals settling downwards from the mantle. This complete slice evidences massive olivine-rich areas with minor amounts of interstitial metal, some metal-rich regions with little olivine, and some regions that contain roughly comparable amounts of metal and olivine grains. This is characteristic of the heterogeneous appearance of the Seymchan pallasite. The olivine-rich regions provide a glimpse of the bottom of the mantle of the parent asteroid where olivine grains crystallized from the silicate melt and settled toward the core. The metal-rich regions represent a portion near the top of the iron-nickel core, beneath the olivine-rich layer at the bottom of the mantle.

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