NWA 18591 Diogenite Meteorite Full Slice, HED Achondrite, 6.57g, Olivine-Bearing from Vesta

An olivine-bearing diogenite full slice from asteroid Vesta

This is a 6.57 gram polished full slice of NWA 18591, a diogenite classified as an olivine-bearing HED achondrite from asteroid 4 Vesta. Diogenites formed deep in Vesta's crust, where minerals settled out of slowly cooling magma, so they are coarser and more orthopyroxene-rich than the basaltic eucrites from the surface. The cut face on this slice shows the brecciated interior of the meteorite: dark orthopyroxene clasts set in a fragmental matrix, with the tan tones of moderate desert weathering across the surface. For background on the type, see our guide on what an achondrite is.

Structure and features of this slice

The polished face reveals a breccia built from millimeter to centimeter sized clasts of orthopyroxene set within a finer fragmental matrix, the record of impact processing on Vesta's surface. Under close light the pyroxene clasts read as dark green to near black, threaded with fine fracture networks, while the surrounding matrix carries the orange and tan coloring of moderate terrestrial weathering. Scattered olivine accompanies the orthopyroxene, which is why the meteorite carries the olivine-bearing designation, and accessory chromite, iron metal, and troilite are present in the rock. The slice is thin and cut through the full width of the stone, and it is shown on an acrylic stand alongside a one centimeter scale cube.

Discovery and provenance

NWA 18591 was found in northwest Africa in 2024 as seven stones with weathered fusion crust, for a total known weight of approximately 610 grams. The stones were acquired from a dealer in Morocco, and the main mass is held by Treasure Coast Meteorite Co. The meteorite was classified by D. Sheikh at the Cascadia Meteorite Laboratory at Portland State University, where a 22.8 gram type specimen is on deposit, and the name was approved by the Meteoritical Society in 2026. This slice therefore comes directly from the holder of the main mass, with provenance that traces to the classifying laboratory. Browse related specimens in our Diogenites collection.

Scientific context

Diogenites are orthopyroxenite achondrites from the deep crust of asteroid 4 Vesta, part of the howardite, eucrite, and diogenite family whose common origin is confirmed by oxygen isotopes, pyroxene chemistry, and the reflectance spectra measured directly at Vesta by NASA's Dawn mission. In NWA 18591 the low-calcium pyroxene has a ferrosilite content of Fs27.8 with a magnesium number of about 72, and the accompanying olivine sits at Fa27.0, values consistent with an olivine-bearing diogenite. The rock records a moderate shock stage, evidence of the impact history that brecciated Vesta's crust and eventually launched this material toward Earth. The classification is published in the Meteoritical Bulletin, No. 115. You can read more about how meteorites earn an official record on our Meteoritical Bulletin explained page.

Frequently asked questions

Is this meteorite authenticated?
Yes. NWA 18591 is an officially classified diogenite recorded in the Meteoritical Bulletin, No. 115, with its main mass held by Treasure Coast Meteorite Co. This slice ships with a Treasure Coast Meteorite Co. certificate of authenticity and is offered by Treasure Coast Meteorite Co., IMCA member #3323.

What is a diogenite?
A diogenite is an orthopyroxene-rich achondrite from the deep crust of asteroid 4 Vesta, coarser grained than the basaltic eucrites that formed at the surface of the same body. Learn more on our Diogenites collection page.

What does olivine-bearing mean here?
The classification notes that this diogenite contains olivine alongside its dominant orthopyroxene. Olivine-bearing diogenites sample slightly different levels of Vesta's cumulate pile than orthopyroxene-only diogenites.

Is it a full slice?
Yes. This is a complete cross-section cut through the full width of the stone and polished, rather than an end cut or fragment.

What is included?
The polished 6.57g full slice shown, on an acrylic display stand, with a Treasure Coast Meteorite Co. certificate of authenticity.

Collector significance

A full slice of a classified diogenite whose main mass is held in house is a strong provenance piece, tying the specimen directly to the meteorite's holder and to the Cascadia Meteorite Laboratory that classified it. The brecciated orthopyroxene texture and the olivine-bearing chemistry make this a representative sample of Vesta's deep crust, a good anchor for an HED suite alongside eucrites and howardites. Full classification data, chemistry, and provenance are published in the Meteoritical Bulletin entry for NWA 18591.