Sericho Pallasite Meteorite Slice, 9.33g, Olivine in Iron-Nickel Matrix

A polished cross-section of the Sericho pallasite

This 9.33g slice of the Sericho pallasite puts one of the most structurally interesting meteorite types directly in hand. The polished face exposes a dense mosaic of olivine crystals suspended in a continuous iron-nickel matrix, the characteristic texture that makes pallasites immediately recognizable and unlike anything else in the natural world. Sericho is notable for its unusually high olivine crystal density, with estimates placing it at 70 to 80% olivine by volume, well above the 50% typical of most pallasites.

The olivine in this specimen has terrestrialized over its time on Earth, shifting from its original green toward amber, brown, and deep black tones. This is a natural and expected consequence of long surface exposure in Kenya's environment, and the resulting color range gives the slice a rich, layered visual character. Metal-rich zones between the crystal clusters show the brushed metallic luster of the iron-nickel alloy, and under magnification the beginning of Widmanstätten structure is visible in areas of coarser metal.

Structure and features

Sericho's olivine crystals are well-rounded to sub-angular, a morphology interpreted as evidence that the crystals were suspended in liquid metal before the pallasite solidified, a snapshot of the boundary zone between an asteroid's metallic core and its rocky mantle at the moment of cooling. The crystal-metal contacts are clean and sharp on the polished face, with individual crystals ranging from a few millimeters to over a centimeter across.

This slice carries a thin protective epoxy coating applied to both faces to stabilize the olivine crystals and slow further terrestrialization. The terrestrialization of the olivine, the progressive oxidation and color shift from green toward brown and black, is visible across the face of this slice. Some crystals retain traces of amber and green in their interiors, visible under direct light at certain angles. The metallic matrix between crystals shows polishing scratches consistent with hand preparation and displays a subdued metallic sheen typical of weathered pallasite metal.

Scientific context

The Meteoritical Bulletin database lists 221 entries in its pallasite category as of September 2026, counted as database entries rather than separate falls. The Meteoritical Bulletin records Sericho simply as a pallasite, without assigning it to the main group or to any other pallasite group.

Sericho was formally recognized in 2016 when large masses were acquired from villagers in Isiolo County, Kenya, though local oral history places knowledge of the stones considerably earlier, camel herders reportedly played on the larger masses as children. The strewn field extends over 45 kilometers, with individual pieces ranging from sub-kilogram fragments to masses as large as 500 kilograms. Learn more about this meteorite type: What Is a Pallasite?

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? Yes. Sericho is an officially classified meteorite with a Meteoritical Bulletin entry. See the official Meteoritical Bulletin entry for Sericho. This specimen ships with a Treasure Coast Meteorite Co. certificate of authenticity. Offered by Treasure Coast Meteorite Co., IMCA #3323.

Why is the olivine dark rather than green? The olivine in Sericho has undergone terrestrialization, a natural oxidation process that occurs as olivine crystals react with Earth's atmosphere and moisture over time. Fresh pallasites have transparent green to amber olivine. Sericho's surface exposure has shifted the color toward brown and black in most crystals, with some retaining amber tones in their interiors. This is characteristic of the Sericho find and does not affect the meteorite's authenticity or scientific significance.

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? The 9.33g polished slice shown, on an acrylic display stand, with a Treasure Coast Meteorite Co. certificate of authenticity. Note: this slice carries a thin protective epoxy coating on both faces.

Collector significance

Pallasites are one of the few meteorite types that require no scientific background to appreciate immediately, the olivine-in-metal texture is visually self-evident and unlike anything terrestrial. The Meteoritical Bulletin records a total known weight of about 2.8 tonnes for Sericho, which is why it is one of the more accessible pallasites for collectors. For collectors building a type collection, a Sericho slice fills the stony-iron category with a properly classified, documented specimen. Browse our full Stony-Iron Meteorites collection.

Meteoritical Bulletin entry: Sericho | Classification: Pallasite | Find, Isiolo County, Kenya, 2016 | Total known weight: ~2,800kg