Sinawan 005 Rumuruti Meteorite Slice, R5-6, 12.51g, Dual Lithology Zones

A Sinawan 005 specimen with contrasting lithology zones

This 12.51g Sinawan 005 specimen presents two visually distinct lithology zones separated by a natural boundary visible across the specimen's face. The darker region exhibits fine-grained matrix with densely packed mineral phases, while the lighter zone shows coarser crystalline texture with more prominent chondrule outlines. This dual lithology structure records different thermal or shock histories within the same meteorite parent body, making each zone a snapshot of separate formation or metamorphic environments. The specimen retains partial fusion crust along one edge, preserving the ablation surface from atmospheric entry.

Rumuruti chondrites are one of the smaller chondrite groups recorded in the Meteoritical Bulletin. Sinawan 005 is one of 3 approved meteorites classified as R5-6, as recorded in the Meteoritical Bulletin database in September 2026. The Bulletin records it as a single stone of 507 g. The R5-6 classification indicates metamorphic grade spanning the transition between type 5 and type 6 equilibration, where mineral compositions approach chemical equilibrium but retain textural evidence of earlier formation stages.

Structure and features

The lithology boundary cuts diagonally across the specimen, creating a natural compositional gradient visible to the naked eye. Chondrules in the lighter zone measure approximately 0.5 to 1.0 millimeters in diameter and show well-defined circular to elliptical outlines, consistent with moderate metamorphic recrystallization. The darker zone displays more homogeneous matrix material with reduced chondrule definition, suggesting higher metamorphic grade or impact processing. Small metal grains distribute throughout both regions, appearing as bright reflective points against the silicate matrix.

The preserved fusion crust segment shows characteristic black glassy texture with flow features oriented parallel to the direction of atmospheric flight. Surface regmaglypts are absent, typical for smaller meteorites that experience shorter atmospheric transit times. The interior material shows no visible weathering, indicating minimal terrestrial alteration since recovery in 2023.

Scientific context

Rumuruti chondrites formed on a parent body distinct from ordinary chondrites, evidenced by their elevated oxidation state, low metal content, and distinctive oxygen isotope signatures. The R-chondrite parent body likely experienced impact disruption and reassembly early in solar system history, creating opportunities for mixing of materials with different thermal histories. This process produces the dual lithology structures observed in specimens like Sinawan 005.

The R5-6 transitional grade indicates peak metamorphic temperatures between 750°C and 950°C, sufficient to homogenize mineral compositions while preserving relict chondrule textures. Rumuruti chondrites contain iron primarily in silicate minerals rather than metal phases, resulting in their characteristic reddish-brown coloration when weathered. Fresh material like this Sinawan 005 specimen shows the true gray to brown tones of unoxidized silicate matrix. Collectors and researchers studying primitive solar system materials find Learn About Meteorites contexts particularly valuable for understanding parent body processes.

Classifier's technical report (not peer reviewed)

J. Garcia of the ADARA Petrography and Curation of Astromaterials Laboratory, who classified Sinawan 005 for the Meteoritical Bulletin, posted a longer description on ResearchGate in July 2025: Petrography, mineral chemistry, and brecciation in Sinawan 005: A Rumuruti chondrite (R5-6) with dual lithologies and low shock stage (technical report, DOI 10.13140/RG.2.2.21146.76487). It is a technical report rather than a journal paper and has not been through peer review, so the Meteoritical Bulletin writeup remains the reviewed record. The report's mineral chemistry matches that writeup exactly: olivine Fa41.4, low-Ca pyroxene Fs25.3, Ca-pyroxene Wo44.7, plagioclase Ab87.3, no iron-nickel metal, pentlandite and magnetite as the opaque minerals, and shock stage S2.

What the report adds. A whole-stone magnetic susceptibility (log chi) of 2.91, at the low end of the range reported for Rumuruti chondrites and consistent with the absence of metal. Garcia interprets Sinawan 005 as a monomict breccia: R5 and R6 material from the same parent body, with the more heavily metamorphosed lithology possibly coming from deeper, hotter levels of that body. He concludes that the two were mixed by low-energy processes rather than a violent impact, and that "the brecciation likely occurred in situ." The report did not measure oxygen isotopes; its support for the Rumuruti classification rests on mineral chemistry, texture and magnetic data.

How to read it. The magnetic susceptibility and the breccia interpretation come from the report, not the Bulletin, and are the classifier's own findings pending peer review. In one section the report describes the lithology boundary as indicative of impact-related brecciation, while its discussion and conclusions favor low-energy, in-situ mixing; the conclusions are given here as the report's final view.

Frequently asked questions

Is this meteorite authenticated? Sinawan 005 is classified in the Meteoritical Bulletin as Rumuruti (R5-6), confirmed through petrographic analysis and mineral chemistry. This specimen includes a certificate of authenticity documenting its classification and provenance. Search the official database: Sinawan 005 MetBull entry.

What does dual lithology mean in this context? Dual lithology refers to two compositionally or texturally distinct regions within a single meteorite specimen. These zones formed through different metamorphic histories or represent separate materials mixed during impact events on the parent body. The visible boundary between zones in this specimen records that mixing or metamorphic transition.

How many Sinawan 005 specimens exist? Sinawan 005 is one of 3 approved meteorites classified as R5-6, as recorded in the Meteoritical Bulletin database in September 2026. The total known weight for all Sinawan 005 material has not been published in the Meteoritical Bulletin.

What is included with this specimen? This listing includes the 12.51g meteorite slice and certificate of authenticity. No display stand is included.

Why are Rumuruti chondrites significant? Rumuruti chondrites sample a parent body chemically distinct from ordinary, carbonaceous, and enstatite chondrite sources. Their oxidation state provides constraints on nebular conditions and planetesimal formation processes not recorded in more common meteorite types.

Collector significance

Sinawan 005 carries documented scarcity: it is one of 3 approved meteorites classified as R5-6, as recorded in the Meteoritical Bulletin database in September 2026. The Bulletin records Sinawan 005 as a single stone of 507 g. The dual lithology structure adds scientific and visual interest beyond typical single-zone specimens, offering collectors a meteorite with research-grade features in a single specimen.

The 12.51g mass provides sufficient size for display while maintaining accessibility compared to larger specimens of similar classifications. Fresh material with minimal weathering preserves original textures and compositions, important for both scientific study and long-term collection value. Collectors building Chondrites or Premium Specimens collections will find few opportunities to acquire R-chondrite material with this combination of a documented approved count, R5-6 classification and distinctive lithology structure.

Meteoritical Bulletin entry: Sinawan 005 | Classification: Rumuruti (R5-6) | Find, Libya, 2023