NWA 17918 Diogenite-pm Meteorite Individual, HED Achondrite with Partial Fusion Crust, 123.55g

A 123.55g individual of NWA 17918 with partial fusion crust

NWA 17918 is classified as Diogenite-pm in the Meteoritical Bulletin, approved 21 December 2025 and published in Meteoritical Bulletin 114 (2026). The writeup gives the classification as HED achondrite (Diogenite, polymict). This is the stone from which the classification section was cut. Treasure Coast Meteorite Co. removed that section and submitted it for classification, and the flat cut face on this specimen is where it was taken. What remains is a 123.55g individual retaining dark fusion crust and regmaglypts across part of its exterior. The photographs show the exact specimen offered.

Structure and features

The cut face shows a pale grey matrix carrying angular white and cream mineral fragments, with tan weathering along the outer rim. Under magnification the clasts are visible as discrete angular grains rather than rounded inclusions, which is the texture expected of a comminuted breccia. Part of the exterior retains dark fusion crust, and elsewhere the surface is weathered to a brown desert patina. The contact between crust and interior is visible on several of the detail images.

Published petrography by Jose Garcia at ADARA describes a polymict breccia composed predominantly, at more than 90 volume percent, of diogenitic material with minor eucritic components. It consists mainly of angular mineral fragments embedded in a fine-grained comminuted matrix. The diogenitic fraction is dominated by low-Ca pyroxene. Ferroan olivine occurs as exotic clasts. The eucritic component is represented by isolated mineral fragments including pyroxene, calcic plagioclase, and a silica polymorph. Accessory phases include chromite and minor FeNi metal.

Published geochemistry from MB 114: ferroan olivine Fa65.5-70.9 (FeO/MnO = 43-45, N=5). Diogenitic components: orthopyroxene Fs28.4-33.3Wo2.9-4.3 (FeO/MnO = 24-31, N=9); pigeonite Fs50.2-68.1Wo6.1-8.3 (FeO/MnO = 31-32, N=5) and Fs64.5Wo18.1 (FeO/MnO = 35); subcalcic augite Fs63.6Wo21.8 (FeO/MnO = 37). Eucritic components: low-Ca pyroxene Fs62.8±0.3Wo2.6±0.4 (FeO/MnO = 33, N=6); calcic plagioclase An83.2-85.0 (N=5). The Bulletin records a magnetic susceptibility of 3.40.

Discovery and provenance

NWA 17918 was found in 2025 in the Adrar region of Algeria. The Bulletin records a total known weight of 996.87g across six stones, and states that the meteorite was purchased from a meteorite dealer. The finder is recorded as anonymous. The type specimen, 20.30g, is held at MUNA, the Museo de la Naturaleza y Arqueologia in Santa Cruz de Tenerife, Spain. Two thin sections are held at ADARA. The remaining mass is with Brian McDonald of Treasure Coast Meteorite Co. Classification was carried out by J. Garcia at ADARA and approved 21 December 2025. The working name recorded in the Bulletin is BMD 019.

The classification section was cut from this stone by Brian McDonald and submitted for classification. The Bulletin does not identify which of the six stones supplied the type specimen, so that connection is recorded here on the authority of Treasure Coast Meteorite Co. rather than the Bulletin. This individual weighs 123.55g, roughly 12 percent of the recorded total known weight for the meteorite.

Scientific context

As of August 2026 the Meteoritical Bulletin database records 77 approved meteorites classified as Diogenite-pm. Diogenites are dominated by orthopyroxene that crystallized slowly at depth within the crust of the asteroid 4 Vesta. The polymict designation for NWA 17918 rests on the coexistence of diogenitic and eucritic pyroxene within the same stone, which the Bulletin states directly as the basis for the classification.

A polymict breccia of this kind records impact mixing: material from more than one crustal level was broken up, combined, and lithified. The ferroan olivine present as exotic clasts is a component that did not originate with the surrounding diogenitic material. Vesta is one of the few asteroids known to have fully differentiated into core, mantle and crust, and NASA's Dawn mission established the spectral link between Vesta and the HED meteorite suite during its 2011 to 2012 orbit. Further background is on our page explaining what an achondrite is.

Frequently asked questions

Is NWA 17918 officially classified? Yes. It is classified as Diogenite-pm in the Meteoritical Bulletin, approved 21 December 2025 and published in Meteoritical Bulletin 114 (2026). Offered by Treasure Coast Meteorite Co., IMCA #3323.

What does polymict mean? A polymict breccia contains fragments of more than one rock type, mixed by impact. For NWA 17918 the Bulletin bases the designation on the presence of both diogenitic and eucritic pyroxene.

Why is there a flat cut face on an individual? This is the stone the classification section came from. Brian McDonald cut that section and submitted it, and the analysis behind the published NWA 17918 entry was performed on material taken from this specimen. What remains is the individual with that single cut surface, exposing the interior breccia while the rest of the original exterior stays intact.

Does this specimen have fusion crust? Yes, in part. Dark fusion crust survives across a portion of the exterior. Other areas are weathered to a brown desert surface, which is normal for a stone recovered in the Sahara.

Where did this meteorite come from? Diogenites are attributed to the asteroid 4 Vesta, the parent body of the howardite, eucrite and diogenite suite. This stone was recovered in the Adrar region of Algeria in 2025.

Collector significance

As of August 2026, 1 of 77 approved meteorites classified as Diogenite-pm, as recorded in the Meteoritical Bulletin database. What sets this specimen apart within that group is its position in the classification itself: the section submitted for analysis was cut from this stone, so the published petrography and geochemistry for NWA 17918 describe material taken from this piece. It remains an individual rather than a cut fragment, retains partial fusion crust, and carries the cut face left by that sampling, showing both the original exterior and the interior in one piece. At 123.55g it accounts for roughly an eighth of the meteorite's recorded total known weight.

This specimen carries serial TC-00033 in the Treasure Coast Meteorite Co. specimen record programme. Its permanent record, with identification data, provenance and photographs, is at Specimen Record TC-00033, and the full index is on the specimen registry.

Browse the full HED Meteorites collection, including the NWA 17918 slices cut from the same fall.

Meteoritical Bulletin entry: Northwest Africa 17918 | Classification: Diogenite-pm | Find, Adrar, Algeria, 2025 | TKW 996.87g | MB 114 (2026) | IMCA #3323