NWA 17918 Diogenite-pm Meteorite End Cut, 13.33g, Polished Breccia Texture from Vesta

Polished window into Vesta's deep crust

This 13.33g polished end cut reveals the complex internal architecture of a polymict diogenite breccia. The mirror-polished surface exposes distinct orthopyroxene-rich clasts set within a matrix of comminuted impact debris, documenting multiple collision events on asteroid Vesta's surface. The cut preserves sharp boundaries between individual fragments, each representing different zones within the asteroid's lower crust or upper mantle. Polishing brings out subtle color variations between clast types and highlights the three-dimensional structure of this impact-assembled rock.

The specimen's form as an end cut provides both a display face showing the full brecciated texture and a natural exterior surface on the opposite side. At 13.33g, this piece offers substantial mass for a diogenite sample while maintaining excellent visual clarity of the polymict structure. The polish reveals grain boundaries and crystal orientations within individual pyroxene fragments.

Orthopyroxene clasts and impact assembly

The dominant mineral phase visible throughout this section is orthopyroxene, the defining component of diogenitic material. Individual clasts range from millimeter-scale fragments to larger domains spanning several millimeters, each showing the characteristic greenish-gray coloration of magnesium-rich pyroxene. These fragments originated as crystallized magma deep within Vesta's interior, later excavated and mixed through violent impact gardening of the asteroid's surface.

The polymict nature becomes evident in the varying crystal sizes and textures between adjacent clasts. Some fragments preserve coarse-grained plutonic textures from slow cooling at depth, while others show finer crystallization patterns. The matrix binding these fragments consists of crushed diogenitic material, lithified through impact compression and heating. This assemblage records the cumulative effect of countless impacts that have processed and reprocessed Vesta's crustal material over 4.5 billion years.

Scientific context

Diogenites represent the deepest crustal samples from asteroid 4 Vesta, the second-largest body in the main asteroid belt. These rocks crystallized from magma chambers several kilometers beneath Vesta's surface during the asteroid's early differentiation. The Dawn spacecraft mission confirmed the connection between HED meteorites and Vesta through spectroscopic mapping and geochemical analysis, making diogenites among the few meteorite types with a confirmed parent body.

The polymict classification indicates this specimen formed through impact brecciation on Vesta's surface, where collisions mixed fragments from different depths and locations within the diogenitic crust. NWA 17918 was classified in 2025, making it one of the most recently recognized members of the diogenite group. Study of such specimens helps planetary scientists understand the internal structure of differentiated asteroids and the processes that have modified their surfaces over billions of years. For broader context on meteorite identification and classification, see our guide on How to Tell if a Rock is a Meteorite.

Frequently asked questions

Is this meteorite authenticated? Yes, NWA 17918 is officially classified as diogenite-pm by the Meteoritical Society. You can verify this classification through the Meteoritical Bulletin entry: NWA 17918. This specimen includes a certificate of authenticity documenting its classification and provenance.

What does polymict (pm) mean? Polymict refers to a breccia containing fragments from multiple source rocks or locations. In this diogenite, polymict texture indicates that impacts on Vesta's surface mixed clasts from different depths or regions within the diogenitic crust, then lithified them into a single rock. The "pm" designation distinguishes this from monomict diogenites, which contain fragments from a single source.

What is included with this specimen? You receive the 13.33g polished end cut and a certificate of authenticity. No display stand is included.

Why is the HED-Vesta connection scientifically important? HED meteorites are the only achondrite group with a confirmed asteroidal parent body, verified by NASA's Dawn mission data. This connection allows scientists to study Vesta's geology through laboratory analysis of meteorites while comparing results to spacecraft observations, providing unique insights into asteroid differentiation and crustal evolution.

How should I display a polished end cut? The polished face shows the internal structure best when viewed flat or at a slight angle under good lighting. Many collectors use small acrylic easels or lean the specimen against a backdrop to showcase both the polished surface and the natural exterior edge.

Collector significance

Diogenite-pm specimens occupy a specialized niche in HED collecting, representing the deepest crustal material from Vesta available to private collectors. Only 74 meteorites carry the diogenite-pm classification, making this subtype substantially rarer than eucrites or howardites. The 13.33g mass provides sufficient size to appreciate the clast structure while remaining accessible compared to larger museum-grade pieces.

The 2025 classification date places NWA 17918 among the newest diogenite additions to the Meteoritical Bulletin, offering collectors an opportunity to acquire recently classified material. The polished preparation reveals structural details invisible on uncut specimens, making this format particularly valuable for collectors focused on understanding impact processes and asteroid geology. This specimen fits well in collections emphasizing Diogenites or broader HED Meteorites representing all three components of Vesta's differentiated crust.

Meteoritical Bulletin entry: NWA 17918 | Classification: Diogenite-pm | Find, Algeria, 2025