Sericho Pallasite Meteorite Full Slice, 103.50g, Polished and Etched

A complete cross section through a Kenyan pallasite, cut from a single stone and finished on both faces. This 103.50 g full slice carries olivine grains distributed through an iron-nickel matrix that has been polished, etched, and sealed with an epoxy coating. The slice is uninterrupted from edge to edge, so the metal and silicate relationship can be read across the whole width of the stone rather than in a fragment of it.

Sericho was recovered from a strewnfield in Isiolo County, Kenya, and classified as a pallasite by L. Garvie, A. Wittmann, and D. Schrader at Arizona State University. The Meteoritical Bulletin records the find year as 2016 and lists the classification in Bulletin 106. As of October 2026, the Meteoritical Bulletin lists this as 1 of 99 approved meteorites classified as Pallasite.

Structure and features

The Bulletin describes Sericho slices as averaging near 70 areal percent olivine, with grains typically 0.5 to 1 cm across and a small number reaching up to 4 cm. Grains are largely rounded and less commonly euhedral, and the published description records them as gemmy green to orange. Both colors are present on this slice, and the transmitted light photograph shows how far light travels through the thinner grains.

This slice was cut deliberately thin, and that is what lets the olivine carry light. How much light passes through an olivine grain depends on how far the light has to travel through it. In a thick pallasite slice the same grains read as dark brown to nearly black, because most of the light is absorbed or scattered by internal fractures before it gets through. Cut thin, the path is short enough for light to pass, and the gemmy green to orange color recorded in the Bulletin shows as a glow when the slice is held up to a window or set in front of a light. Iron is the main element that colors olivine, and Sericho olivine is published at Fa12.3, a magnesium rich composition light enough in tone to glow at this thickness.

A thin cut is also the harder cut. Pallasite olivine is brittle and often fractured, and the thinner the slice, the less metal there is around each grain to hold it in place. Grains can crack or drop out during sawing and polishing, so a full slice that comes through this thin with its olivine intact takes more time and more care than a thick one.

A fine straight saw line crosses the reverse face and is visible in the close up photographs. It was left by the blade during cutting and is a surface mark, not a fracture through the specimen.

The metal is dominated by swathing kamacite around the olivine, with pockets of dark-etching plessite. Etching brings out that structure as tonal contrast across the matrix rather than as a single uniform figure. The Bulletin notes that a well developed Widmanstatten pattern appears only in the occasional metal-rich region of Sericho, so this is a slice to read for its metal and silicate architecture rather than for a classic crossed-band figure.

Accessory troilite and schreibersite are recorded in the classification, along with under 1 areal percent chromite. Weathering grade is stated as low, which is consistent with the surface recoveries described in the Bulletin writeup.

Discovery and provenance

The published history records that in 2016 two brothers searching for their camels came across several large dense stones west of Habaswein and south of Sericho. There are no rocks in that area, so they concluded the masses were meteorites and spent several weeks recovering them with engine hoists. The stones had been known to camel herders for decades before that. One village elder recalled playing on top of them as a child.

In early January 2017 Michael Farmer received a photograph of a 107 kg pallasite, traveled to Nairobi, and purchased the stone. He returned two weeks later with Moritz Karl and was shown more than a ton of material stacked in two house compounds. The Bulletin records more than 2,800 kg found to date across a strewnfield over 45 km long, with individual masses ranging from under 1 kg to 500 kg. The type specimen of 48 g is held at Arizona State University, and the main mass is recorded with Michael Farmer, Moritz Karl, and Thomas Strope.

This specimen was acquired by Treasure Coast Meteorite Co. and prepared in house.

Scientific context

Pallasites pair olivine, a mantle silicate, with iron-nickel metal of the kind found in asteroid cores. Explaining how the two came to sit together in one rock is the central question the class poses, and the leading models involve mixing at a core and mantle boundary or the injection of molten metal into olivine during a large impact. Either way, a pallasite slice shows two parts of a differentiated asteroid that ordinarily never touch.

The olivine composition for Sericho is published as Fa12.3 plus or minus 0.1, with kamacite at 7.1 plus or minus 0.6 weight percent nickel. Those are measured values from the classification work, not estimates from appearance, and they are what distinguishes one pallasite from another once the stones are cut.

Background on the class is set out in what is a pallasite, and the etched metal structure is covered in the Widmanstatten pattern explained.

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 a full slice or a part slice?
A full slice. The cut runs the complete width of the stone, so the natural exterior margin is present all the way around the specimen rather than on one side only.

What is the coating, and does it affect the stated weight?
The finished faces are sealed with a clear epoxy coating. Pallasites contain iron-nickel metal, which corrodes in humid air if left bare, and the olivine grains sit in that metal, so a sealed surface protects both. The stated 103.50 g is the weight of the specimen as offered, coating included. Epoxy is a permanent treatment and is not intended to be removed.

Why is the slice cut so thin
So the olivine transmits light. Thick pallasite slices show their olivine as dark grains, while a thin slice lets light pass through each crystal and brings out its green to orange color. The tradeoff is that thin slices are harder to cut and to finish without losing grains.

What is the straight line across the face
A saw mark left during cutting. It is visible in the close up photographs, sits in the finished surface, and is not a crack or fracture through the slice.

Will I see a Widmanstatten pattern?
Not as a bold crossed-band figure across the whole face. The Meteoritical Bulletin records that a well developed Widmanstatten pattern appears only in the occasional metal-rich region of Sericho. What the etch shows here is the swathing kamacite around the olivine grains and the darker plessite pockets between them.

Why is a total known weight of 2.8 tonnes quoted for a meteorite sold in gram sizes?
That figure is the recorded mass for the entire Sericho strewnfield, which extends more than 45 km and has produced many separate stones. It describes the find as a whole and says nothing about the size of any one specimen.

How do I verify the classification?
The entry is public. See the Meteoritical Bulletin Database entry for Sericho, and understanding the Meteoritical Bulletin for how to read it. Treasure Coast Meteorite Co. is an IMCA member, number 3323.

Collector significance

Pallasite is a small class. As of October 2026 the Meteoritical Bulletin lists 99 approved meteorites classified as Pallasite, with no group assigned, out of more than 80,000 approved meteorites. Sericho is one of the few that has been recovered in enough quantity, and in good enough condition, to be cut into display slices at all, which is why it has become the pallasite most collectors meet first.

A full slice at 103.50 g sits above the small end of that market. The complete cross section, both finished faces, and the intact natural margin make it a specimen that can be handled and displayed from either side. Other stony-iron material is listed in the stony-iron meteorite collection, and general background is indexed on the learn hub.

The thin cut is what sets this slice apart as a display piece. Placed against a window or in front of a light source, the olivine shows its color through the full width of the stone instead of reading as dark grains in metal.

Classification data on this page is reproduced from the Meteoritical Bulletin Database entry for Sericho, published in Meteoritical Bulletin 106.