Sericho Pallasite Meteorite Slice, 17.39g, Olivine Crystal Mosaic

Olivine crystal density in a compact pallasite slice

This 17.39g slice exposes the classic pallasite architecture: olivine crystals distributed through a continuous iron-nickel matrix. The polished face shows crystal clusters separated by metal veins, with the olivine occupying an estimated 70 to 80% of the total volume. Individual crystals range from several millimeters to just over one centimeter across, well-rounded to sub-angular in form.

The olivine has terrestrialized during surface exposure in Kenya, shifting from green toward amber, brown, and deep black. Metal zones between crystal clusters display the brushed metallic luster characteristic of the kamacite-taenite alloy. Both faces carry a thin epoxy coating applied to stabilize the olivine and slow oxidation.

Structure and features

Crystal morphology in this slice reflects the pallasite formation environment: olivine grains set in metal, a texture long interpreted as forming near the boundary between a differentiated asteroid's core and mantle. The rounded edges of larger crystals suggest partial resorption in the melt phase before final solidification. Metal-olivine contacts are clean and sharply defined where the polish exposes them.

Terrestrialization progresses from the crystal edges inward, visible as color gradients within individual grains. Some crystals retain translucent amber cores under direct light, surrounded by darker oxidized rims. The metal matrix shows no visible corrosion under the epoxy layer.

Scientific context

Pallasites have long been interpreted as samples from the core-mantle boundary of a disrupted asteroid, though more recent studies have proposed other origins and the question remains open. Pallasites account for less than 0.2% of all classified meteorites. Sericho was recovered from a strewn field extending over 45 kilometers in Isiolo County, Kenya, with formal recognition following in 2016. Learn About Meteorites

The story

Sericho’s recovery began with lost camels. According to the Meteoritical Bulletin, in 2016 two brothers searching for their animals west of the village of Habaswein, south of Sericho in eastern Kenya, came across several large, unusually dense stones. There are no rocks in that area, so they decided the stones were meteorites, and they spent several weeks moving them home to Habaswein with engine hoists.

The stones were not new to the people who lived there. The Bulletin records that camel herders had known about the masses for decades, and that one village elder remembered playing on top of them with his brothers when he was a child.

In early January 2017, Michael Farmer received an email with a photo of a 107 kg “giant pallasite,” travelled to Nairobi and bought it. Two weeks later he returned to Kenya with Moritz Karl and went to Habaswein, where they were shown more than a ton of specimens stacked in the courtyards of two house compounds. The Bulletin records that more than 2,800 kg has been found to date.

Source: Meteoritical Bulletin entry for Sericho, writeup from MB 106.

What the research reports

The Meteoritical Bulletin classifies Sericho as a pallasite without assigning it to a group. The original classification in Meteoritical Bulletin 106 reported olivine and metal chemistry, including olivine Fa12.3 with an FeO/MnO ratio of 57.4, but did not include the oxygen isotope or bulk metal trace-element data normally used to place a pallasite in a group. Later peer-reviewed studies have analyzed Sericho as a main group pallasite. Their findings come from the authors' own samples and methods, not from the Bulletin, and are given here as the studies state them. Until the Bulletin entry is updated, this listing uses the official classification.

Windmill et al. (2022): oxygen isotopes match the main group

R. J. Windmill, I. A. Franchi, J. L. Hellmann, J. M. Schneider, F. Spitzer, T. Kleine, R. C. Greenwood and M. Anand, of The Open University, the University of Münster, the Max Planck Institute for Solar System Research and the Natural History Museum, London, published Isotopic evidence for pallasite formation by impact mixing of olivine and metal during the first 10 million years of the Solar System (PNAS Nexus, volume 1, pgac015, 2022).

Oxygen isotopes. Two Sericho olivine samples gave Δ17O values of −0.202 and −0.200 per mil, within the average the authors report for main group pallasite olivine of −0.197 ± 0.016 per mil. The study places Sericho with Seymchan in a low aluminium and manganese subgroup, noting that "Sericho and Seymchan exhibit variable olivine–metal ratios yet have unresolvable Δ17O values."

Formation. The authors found an oxygen isotope mismatch between olivine and chromite in main group pallasites. They interpret it as evidence that the metal and the olivine came from two different bodies brought together by an impact, rather than forming together at a single core-mantle boundary.

Jung et al. (2026): weathering and magnetism

J.-I. Jung, S. Gaal, S. M. Tikoo, E. Lopes, J. Mells, D. H. Burns and R. G. Hatfield, of Stanford University, the University of Alabama and the University of Florida, published Magnetization records of terrestrial weathering in the Sericho pallasite (Meteoritics & Planetary Science, 2026).

Classification in the study. The authors describe their sample as "the main group Sericho pallasite."

Findings. Their sample contained fine magnetite grains inside iron oxide veins, likely goethite, formed by alteration after the meteorite reached Earth. The authors conclude that this secondary material dominates the sample's magnetic signal, so it cannot be used to recover the parent body's magnetic field, and they note that different samples of one meteorite can weather to very different degrees.

Frequently asked questions

Is this meteorite authenticated? Sericho is classified in the Meteoritical Bulletin as a pallasite, with no group assigned. You can verify the classification here: Meteoritical Bulletin search for Sericho. This specimen includes a certificate of authenticity.

Is Sericho a main group pallasite? The Meteoritical Bulletin classifies Sericho as a pallasite without assigning a group, because the original classification did not include the oxygen isotope or metal trace-element data used to assign one. Later peer-reviewed studies have analyzed Sericho as a main group pallasite, and its olivine oxygen isotope values match the main group. Until the Bulletin entry is updated, this listing uses the official classification.

What is included with this specimen? This listing includes the 17.39g slice and a certificate of authenticity. No display stand is included.

Why is the olivine brown instead of green? Terrestrialization: oxidation of olivine during surface exposure in Earth's atmosphere. This is a natural process in all recovered pallasites and does not affect scientific value or structural integrity under the protective epoxy coating.

Can this slice be backlit? Olivine in Sericho is typically too oxidized for effective backlighting. The terrestrialized crystals appear opaque to dark brown under transmitted light. Metal content also blocks light transmission. This slice exhibits some translucence and is suitable for a backlighting display.

Collector significance

Pallasites remain the most visually distinctive meteorite type collectors can acquire, and Sericho offers accessibility to this category due to the large recovered mass and extended strewn field. This 17.39g slice balances size and price point while retaining the diagnostic olivine-metal texture. The high olivine fraction makes Sericho slices denser in crystal coverage than many other pallasites.

Compact slices like this one serve well in organized collections where space constraints matter. The epoxy coating ensures stability over time, addressing the primary long-term preservation concern with pallasite specimens. Browse additional pallasite specimens: Stony-Iron Meteorites.

Meteoritical Bulletin entry: Sericho | Classification: Pallasite | Find, Kenya, 2016