Seymchan Pallasite Meteorite Full Slice, PMG, 591.00g, Widmanstätten Pattern

591g full slice from the iron-dominant zone with crisp Widmanstätten banding edge to edge

This 591.00g Seymchan full slice is cut from the iron-dominant zone of the mass, presenting no olivine. The Widmanstätten pattern reads across the entire face without interruption. Kamacite bands are sharply delineated throughout, the geometric interlocking structure is consistent from edge to edge, and there is no significant oxidation compromising the etched surface. The specimen is large enough that the crystal geometry registers at a glance rather than requiring close inspection.

Structure and features

The Widmanstätten pattern in this slice formed as the parent body cooled over millions of years deep inside a differentiated asteroid. The process produced an interlocking lattice of kamacite and taenite, two iron-nickel alloys that precipitate at different temperatures and lock into geometric bands as the system slowly equilibrates. The structure cannot be produced artificially and is one of the definitive indicators of iron meteorite authenticity. The banding width visible in this slice is consistent with the iron-dominant zones of Seymchan, which was classified as an iron prior to its reclassification as a pallasite, and the geometry is uninterrupted across the full face.

Due to Seymchan's heterogeneous internal structure, specimens fall into two distinct categories: those from olivine-bearing zones containing silicate crystal clusters, and those from iron-dominant zones consisting almost entirely of nickel-iron metal. This slice is from the iron-dominant zone. Both zone types are scientifically documented within the same classified meteorite.

Scientific context

Seymchan was found in June 1967 by geologist F. A. Mednikov in the dry bed of the Hekandue river, a left tributary of the Yasachnaya in Magadan Oblast, Russia. The main mass of 272.3 kg was recovered during a geological survey. A second specimen of 51 kg was located nearby in October 1967. Both masses were turned over to the Academy of Sciences of the USSR. The meteorite was first recorded as an iron in Meteoritical Bulletin 43 (1968), later catalogued as IIE and then as an ungrouped iron.

In 2004, Dmitri Kachalin recovered additional material from the original find area, and approximately 20% of the new specimens were found to contain olivine crystals. This revealed the pallasitic nature of the mass. Van Niekerk et al. formally reclassified Seymchan as a pallasite in 2007. For further reading on pallasite formation and structure, see our guide: What Is a Pallasite?

Frequently asked questions

Is this meteorite authenticated? Yes. Seymchan is classified in the Meteoritical Bulletin as Pallasite, PMG. You can verify the classification here: Seymchan. This specimen ships with a certificate of authenticity from Treasure Coast Meteorite Co. (IMCA #3323).

What does PMG mean? PMG stands for pallasite main group, the dominant chemical grouping among pallasites. Seymchan was reclassified as a main group pallasite (Pallasite, PMG) following the identification of olivine-bearing zones in recovered material studied by van Niekerk et al. (2007).

Why does this slice have no olivine if Seymchan is a pallasite? Seymchan is structurally heterogeneous. Some zones of the mass contain olivine crystal clusters; others consist almost entirely of nickel-iron metal. This slice is cut from an iron-dominant zone. Both zone types are authentic and represent the same classified meteorite.

What care does an etched iron meteorite slice require? Store in a low-humidity environment. Periodic application of Renaissance Wax or food-grade mineral oil to the etched face will slow oxidation. Avoid handling with bare hands and keep away from moisture sources.

What is included with this specimen? The 591.00g Seymchan full slice and a certificate of authenticity with full classification details from Treasure Coast Meteorite Co. (IMCA #3323).

How do I verify this is the same specimen shown in these photographs?
This stone is recorded under serial TC-00020. Its specimen record is a permanent page holding the classification data as published in the Meteoritical Bulletin, the recorded weight, and photographs of this exact stone. Meteorite surfaces, cut faces and clast patterns are individual to each stone, so a specimen in hand can be compared against those photographs and weighed against the recorded figure.

Collector significance

Full slices of Seymchan at this size are not commonly available. Most material on the collector market comes as smaller partial slices, end cuts, or fragments. At 591g and over 20 cm in length, this specimen represents a substantial section of the mass. The full-slice format is what best displays Widmanstätten structure at scale, and in this specimen the geometry is uninterrupted from edge to edge with no significant oxidation or surface compromise. The iron-dominant zone is the material that most clearly expresses the structural identity recorded when Seymchan was classified as an iron, and that structure is the primary visual feature of this slice.

Seymchan occupies a specific position in the collector market as a pallasite with two visually distinct specimen types from the same classified mass. Collectors working across meteorite categories often target both. This slice represents the iron-dominant type in a format and at a size that is increasingly difficult to source as original stock is cut down and dispersed.

Meteoritical Bulletin entry: Seymchan | Classification: Pallasite, PMG | Find, Russia, 1967

Specimen record

This specimen is serialized as TC-00020 and is issued with a certificate card bearing that serial. The serial indexes a permanent public record maintained by Treasure Coast Meteorite Co., and every issued serial is listed in the Specimen Registry.

What the research reports

The Meteoritical Bulletin classifies Seymchan as a main group pallasite (Pallasite, PMG). The entry records how that classification changed over time: Iron in Meteoritical Bulletin 43 (1968), IIE in the Natural History Museum Catalogue of Meteorites (2000), and Iron-ung in MetBase (2006), before the reclassification that followed van Niekerk et al. (2007). The Bulletin lists the total known weight as 323.3 kg, while the original 1968 writeup gave about 351 kg for the first two masses. The findings below come from the authors’ own samples and methods, not from the Bulletin, and are given here as the studies state them.

van Niekerk et al. (2007): from iron to pallasite

D. van Niekerk, R. C. Greenwood, I. A. Franchi, E. R. D. Scott and K. Keil, of the University of Hawaii and The Open University, presented Seymchan: A main group pallasite, not an iron meteorite at the 70th Annual Meteoritical Society Meeting (abstract 5196, 2007).

Same meteorite. A 2004 expedition to the original site recovered more masses, and reports suggested about a fifth of them were pallasitic. Neutron activation analysis showed the pallasite metal is identical in composition to the original iron masses, confirming that they belong to the same meteorite.

Classification. Oxygen isotopes in the olivine fall within the main group field, and the metal composition groups Seymchan with the main group. The authors add that its high iridium “indicates that it is anomalous (PMG-am),” a finer distinction than the Bulletin’s PMG classification records.

Windmill et al. (2022): oxygen isotopes

The PNAS Nexus study Isotopic evidence for pallasite formation by impact mixing of olivine and metal during the first 10 million years of the Solar System, by R. J. Windmill and colleagues at The Open University, the University of Münster, the Max Planck Institute for Solar System Research and the Natural History Museum, London, places Seymchan in a low aluminium and manganese subgroup of the main group pallasites. It notes that Seymchan and Sericho have oxygen isotope values that cannot be told apart despite their different olivine to metal ratios, and it interprets main group pallasites as mixtures of olivine and metal from two different bodies brought together by an impact.