Sinawan 005 Rumuruti Meteorite Slice, R5-6, 22.82g, Dual Lithology Zones

Dual lithology R-chondrite with visible compositional boundaries

This Sinawan 005 slice displays sharp boundaries between light and dark lithologies within a single 22.82g specimen. The contrasting zones represent different thermal metamorphic grades preserved in the same meteorite, a diagnostic feature of R5-6 classification. The light region shows coarser-grained recrystallization while the darker zone retains finer textures, visible across the entire face of the slice. Sinawan 005 is one of 3 approved meteorites classified as R5-6, as recorded in the Meteoritical Bulletin database in September 2026.

Rumuruti chondrites are one of the smaller chondrite groups recorded in the Meteoritical Bulletin. This specimen was recovered in Libya in 2023 and classified by J. Garcia at ADARA, approved on 8 July 2025 and published in Meteoritical Bulletin 114. The R5-6 designation indicates metamorphic grades straddling petrologic types 5 and 6, reflecting complex thermal history in the parent body interior.

Structure and features

The slice reveals two distinct lithologic domains separated by a visible transition zone. The lighter region occupies approximately 60% of the specimen face and displays homogenized mineral grains consistent with type 6 metamorphism. The darker domain retains partial chondrule structure and finer matrix material characteristic of type 5. This textural heterogeneity within a single stone indicates impact mixing or incomplete thermal equilibration on the parent body.

Olivine grains in both zones show the iron-rich composition typical of Rumuruti chondrites, distinguishing them from ordinary and carbonaceous types. The slice surface has been prepared to highlight the boundary between lithologies without obscuring internal structure. Minor weathering fractures cross both domains, consistent with terrestrial residence time in the Sahara.

Scientific context

Rumuruti chondrites formed on a distinct parent body separate from ordinary, enstatite, and carbonaceous chondrite sources. Oxygen isotope data place R-chondrites outside the terrestrial fractionation line, consistent with a parent body distinct from those of the ordinary chondrites. The high oxidation state and iron-rich olivine composition suggest formation in a different region of the early solar system compared to more common meteorite types.

The dual lithology nature of Sinawan 005 specimens indicates the parent body experienced localized heating events or impact-driven mixing after initial formation. Type 5-6 metamorphism requires sustained temperatures between 700 and 950 degrees Celsius, likely achieved through internal radiogenic heating or large impact events. Understanding these transitional types helps constrain thermal evolution models for small planetary bodies. Learn About Meteorites to explore how different chondrite groups relate to solar system formation 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 as Rumuruti (R5-6) in the Meteoritical Bulletin Database. You can verify the classification at Meteoritical Bulletin entry for Sinawan 005. A certificate of authenticity documenting the classification accompanies this specimen.

What does R5-6 classification mean? The R designation identifies this as a Rumuruti-type chondrite, a group characterized by iron-rich olivine. The 5-6 indicates the specimen contains material from two metamorphic grades: type 5 with partial recrystallization and type 6 with complete thermal equilibration. This dual classification reflects heterogeneous heating history preserved in the meteorite.

What is included with this specimen? You receive the 22.82g slice shown in the photographs and a certificate of authenticity. No display stand is included.

How many R5-6 meteorites are known? Sinawan 005 was found in Libya and approved in July 2025, making it a recent discovery. The Meteoritical Bulletin records a single stone of 507 g, and sinawan 005 is one of 3 approved meteorites classified as R5-6, as recorded in the Meteoritical Bulletin database in September 2026. R5-6 is an uncommon petrologic type among the Rumuruti chondrites.

How should I display this dual lithology specimen? The contrasting zones are visible from both sides of the slice. Positioning under directional lighting enhances the boundary between light and dark domains. The specimen displays well in standard meteorite holders or acrylic stands that allow viewing of the entire prepared surface.

Collector significance

Rumuruti chondrites represent less than 0.5% of the meteorite collection population, making any R-type specimen a priority acquisition. Sinawan 005 adds documented scarcity as one of 3 approved R5-6 meteorites. The dual lithology feature provides immediate visual distinction from uniform chondrites and offers a tangible example of incomplete thermal processing.

The 22.82g size permits detailed examination of both lithologic zones while remaining display-friendly for cabinet collections. Scientific documentation in published literature adds research provenance beyond standard Meteoritical Bulletin classification. Collectors focusing on Chondrites or building comprehensive type collections will find limited future opportunities to acquire Sinawan 005 material. For those interested in diverse compositional groups, explore our Stony Meteorites collection.

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