NWA 18048 Eucrite-pmict Meteorite Slice, 133.72g, Mirror Polished, HED Achondrite from Vesta

Clast boundaries revealed through mirror polish

This 133.72-gram slice of NWA 18048 presents a textural mosaic of eucritic fragments embedded in a darker groundmass. The mirror polish transforms the cut surface into a display of compositional contrasts, where lighter clasts stand against melt-rich matrix zones. Boundaries between fragments appear sharp in some areas and diffuse in others, recording different stages of impact mixing and thermal processing.

The specimen's size and finish make the internal architecture immediately legible. Fragment shapes range from angular to subrounded, suggesting variable transport histories before final consolidation. Dark matrix material fills interstitial spaces, creating a framework that holds the clast population together while preserving evidence of the mechanical forces that assembled this breccia.

The polishing reveals subtle color gradations within individual clasts, hinting at mineralogical variation between basaltic components. This level of visual detail transforms the specimen from a geological sample into a readable record of asteroid surface processes.

Structure and features

Polymict texture dominates this specimen, with clast sizes varying from millimeter-scale fragments to larger blocks several centimeters across. The clast population consists primarily of basaltic material with varying grain sizes, reflecting different cooling histories from the parent body's volcanic past.

Matrix material between clasts appears fine-grained and darker than the enclosed fragments. Some matrix zones show flow textures consistent with impact melt, while others display granular character suggesting mechanical mixing of crushed material. The polish brings out these textural differences by eliminating surface roughness that would otherwise obscure subtle structural boundaries.

Certain clasts display internal crystalline structure visible under magnification, while others appear more homogeneous. This variation records the diverse crustal environments that contributed material to this breccia. No fusion crust remains on this interior slice, which was removed from a larger mass during laboratory preparation.

Scientific context

NWA 18048 belongs to the HED achondrite group, a meteorite family tied to asteroid 4 Vesta through spectroscopic data collected by NASA's Dawn mission. Eucrites represent the basaltic crust of this body, formed through volcanic processes after the asteroid differentiated into core, mantle, and crust approximately 4.56 billion years ago.

The polymict classification indicates this specimen formed through regolith processes rather than as a simple igneous rock. Repeated impacts fractured Vesta's surface, mixed crustal fragments, and created layers of debris that were later compacted and lithified. Some polymict eucrites incorporate impact melt, creating a hybrid rock that records both volcanic and collision histories.

This dual record makes polymict eucrites valuable for understanding asteroid surface evolution. They demonstrate how impact cratering reworks planetary crusts, creating new rock types through mechanical and thermal processes. For broader context on meteorite types and formation, see our Learn About Meteorites page.

Frequently asked questions

Is this meteorite authenticated? Yes. NWA 18048 is classified as eucrite-pmict in the Meteoritical Bulletin Database maintained by the Meteoritical Society. You can verify this classification by searching the official database. Each specimen includes a certificate of authenticity documenting its classification and provenance.

What does polymict mean? Polymict (pmict) indicates a brecciated meteorite containing fragments from multiple source rocks. In this eucrite, polymict texture results from impact processes that mixed different basaltic components on Vesta's surface before the material was lithified into a consolidated breccia.

What is included with this specimen? You receive the 133.72g mirror-polished slice and a certificate of authenticity. No display stand is included unless explicitly noted in the product listing.

How is this connected to asteroid Vesta? Spectroscopic observations by NASA's Dawn spacecraft confirmed that Vesta's surface composition matches the HED meteorite group. Eucrites like NWA 18048 are fragments of Vesta's basaltic crust, ejected by impacts and delivered to Earth as meteorites.

Why does the polish matter? Mirror polishing removes surface texture and oxidation, revealing internal structure with maximum clarity. Clast boundaries, matrix composition, and color variations become visible in ways that rough or weathered surfaces cannot show.

Collector significance

Eucrite slices appeal to collectors seeking specimens with clear internal structure and confirmed asteroid origins. The mirror polish on this piece maximizes visual information, making it equally suitable for display and study. At 133.72 grams, the specimen offers substantial size while remaining within accessible price ranges for HED material.

Polymict eucrites occupy a specific niche within collections focused on differentiated bodies. They complement simple eucrites by showing how impact processes rework and complicate igneous rocks. The visible clast population in this specimen provides immediate evidence of that reworking, making the geological story accessible without microscopy.

For collectors building HED suites, polymict eucrites add textural diversity alongside cumulate and basaltic end members. Browse additional specimens from Vesta in our Eucrites and HED Meteorites collections.

Meteoritical Bulletin entry: NWA 18048 | Classification: Eucrite-pmict | Find, Northwest Africa, 2024