NWA 18048 Eucrite-pmict Meteorite Slice, 119.29g, Mirror Polished Impact Breccia

Impact-fused crustal fragments from asteroid 4 Vesta

This 119.29g eucrite-pmict slice preserves a frozen record of ancient impact violence on Vesta's surface. Mirror polishing on one face reveals a complex mosaic where light and dark lithologies meet along sharp clast boundaries, interrupted by thick melt veins that flow through the matrix. The polymict texture shows fragments of different eucritic materials welded together during collision events that fractured and re-cemented Vesta's basaltic crust billions of years ago.

The mirror finish brings exceptional clarity to features that would remain obscure in a natural or lightly polished surface. Clast edges stand in sharp relief against the surrounding matrix. Melt zones appear as dark, glassy regions where impact energy temporarily liquefied the rock. The size of this slice provides room to observe how different components relate spatially across the specimen, offering a window into the mechanical mixing processes that shaped Vesta's regolith.

At nearly 120 grams, this specimen represents a substantial example of classified polymict eucrite material. Complete slices of this size with professional mirror preparation occur infrequently in the collector market, particularly from meteorites with total known weights measured in single-digit kilograms.

Clast boundaries and impact melt features

The slice displays distinct eucritic clasts ranging from light gray to nearly black, each fragment representing a different episode of volcanism or impact processing on Vesta. Where clasts meet, boundaries range from sharp fracture lines to gradational zones where impact heating partially melted and mixed adjacent materials. The mirror polish reveals crystalline structure within individual clasts, showing the original igneous texture of Vestan basalt frozen at various cooling rates.

Melt veins cut across clast boundaries in multiple orientations, recording separate impact events that fractured already-brecciated material. These veins appear darker than surrounding clasts due to rapid quenching from molten to solid state. Some melt zones reach several millimeters in width, indicating significant local heating. The distribution of melt throughout the slice suggests this material comes from a zone that experienced repeated impact gardening rather than a single catastrophic collision.

Shock features visible under magnification include planar fractures in pyroxene crystals and deformation textures along grain boundaries. The preservation of these features alongside the coarse clast structure indicates shock pressures sufficient to melt and mix without completely homogenizing the original components.

Basaltic volcanism and the HED parent body

Eucrites formed from magma oceans on asteroid 4 Vesta approximately 4.565 billion years ago, shortly after solar system formation. As Vesta's interior differentiated, less dense silicate melts rose to form a basaltic crust while metal and dense silicates sank toward the core. The eucritic clasts in this specimen represent fragments of that ancient crust, each potentially from different lava flows or plutonic intrusions that crystallized at varying depths and cooling rates.

The polymict classification indicates this meteorite consists of multiple lithologic components mixed through impact gardening. Vesta's lack of atmosphere and geological activity meant that impacts remained the sole mechanism for reworking surface materials over billions of years. Each collision fractured bedrock, ejected material, and deposited mixed ejecta that became lithified through compression and impact heating. The clasts in NWA 18048 may have originated kilometers apart on Vesta's surface before being combined in the impact event that created this breccia.

NASA's Dawn mission confirmed Vesta as the HED parent body through detailed spectral mapping and crater analysis. Dawn data showed that major impact basins excavated deep enough to expose subsurface lithologies and create extensive ejecta blankets of mixed material. This specimen likely formed in such an environment before being launched into space by a subsequent impact energetic enough to overcome Vesta's gravity. For more context on how scientists identify and classify space rocks, visit our guide: Learn About Meteorites.

Frequently asked questions

Is this meteorite authenticated? NWA 18048 received official classification as eucrite-pmict through analysis and submission to the Meteoritical Society. The classification appears in the Meteoritical Bulletin Database: NWA 18048. This specimen includes a certificate of authenticity documenting its provenance and classification.

What does polymict mean in eucrite-pmict? Polymict indicates the specimen contains clasts of different lithologic types mixed together, as opposed to monomict breccias where all fragments come from the same parent rock. In eucrites, this typically means multiple generations of basaltic material combined through impact gardening on Vesta's surface. The "pmict" abbreviation distinguishes these impact breccias from single-lithology eucrites that cooled as intact igneous bodies.

What is included with this specimen? You receive the 119.29g mirror-polished slice shown in the photographs and a certificate of authenticity. No display stand is included unless separately noted.

Why is this specimen mirror polished? Mirror polishing reveals internal structure that remains hidden in rough or naturally weathered surfaces. The technique uses progressively finer abrasives to create an optically flat surface that shows clast boundaries, melt veins, crystal structure, and compositional variations with maximum clarity. For eucrite-pmict specimens, mirror finishing is the optimal preparation method to display the complex brecciation that defines the classification.

How did this meteorite reach Earth from Vesta? Large impacts on Vesta eject material at velocities exceeding the asteroid's escape velocity (approximately 360 meters per second). Ejected fragments enter independent solar orbits until gravitational interactions or additional collisions alter their trajectories. Some eventually intersect Earth's orbit. The time between ejection and Earth arrival can range from hundreds of thousands to millions of years. Cosmic ray exposure studies on HED meteorites suggest typical transit times of several million years.

Display-grade specimen from a restricted inventory

Large mirror-polished eucrite slices appear infrequently in the collector market. Most polymict eucrite material available consists of small fragments, partial slices, or unpolished end cuts. Complete slices exceeding 100 grams with professional mirror preparation represent a small fraction of available inventory across all dealers. The preparation quality in this specimen—flat polishing without edge rollover, uniform finish, preserved clast structure—indicates experienced laboratory work rather than amateur processing.

This piece functions equally well as a research reference, teaching specimen, or display centerpiece. The size provides enough surface area to observe multiple melt generations and clast relationships simultaneously, while the mirror finish allows direct observation of mineralogy and texture under magnification. Collectors focusing on differentiated asteroids, impact processes, or eucrites specifically will find this specimen demonstrates key features of polymict impact breccias from Vesta's ancient crust. For those building comprehensive HED collections, substantial polymict examples complement monomict eucrites and diogenites by illustrating the mechanical mixing processes that dominated Vesta's surface evolution. Browse our full selection of Vestan materials: HED Meteorites.

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