Sinawan 005 Rumuruti Meteorite Slice, R5-6, 17.32g, Dual Lithology Zoning

Dual lithology zones preserved in a type 5-6 R-chondrite

This 17.32g slice of Sinawan 005 shows two distinct lithology zones across its cut surface—a light-toned region and a darker zone with contrasting mineral composition and thermal history. The boundary between these zones represents heterogeneous metamorphic conditions within the parent body, where discrete regions experienced different peak temperatures during thermal processing. Rumuruti chondrites record metamorphic grades from unequilibrated type 3 through highly equilibrated type 6, and specimens straddling this R5-6 boundary preserve evidence of transitional heating events. The slice displays well-defined chondrules embedded in both lithologies, with the darker zone showing more advanced recrystallization of the matrix.

Only three specimens of Sinawan 005 have been classified and entered into the Meteoritical Bulletin following the 2023 recovery in Libya. This slice represents a significant fraction of the known material available to private collectors. The dual lithology feature makes this specimen scientifically noteworthy—most R-chondrites show relatively uniform metamorphic grade across individual stones, while this piece captures a structural discontinuity that likely formed during complex parent body evolution.

Chondrule preservation and matrix structure

Chondrules remain visible throughout both lithology zones, with sizes ranging from submillimeter to approximately 1mm in diameter. The lighter zone preserves more distinct chondrule boundaries, indicating lower metamorphic grade consistent with R5 classification. The darker zone shows partial to complete recrystallization of chondrule mesostasis into granular texture, characteristic of the R6 grade. Olivine grains display a distinctive rusty-red oxidation state typical of Rumuruti chondrites, caused by high oxidation conditions during formation. Metal content appears minimal, as expected for R-chondrites, which contain less than 1% metallic iron-nickel by volume.

The matrix surrounding the chondrules consists of fine-grained olivine and pyroxene crystals, with the darker lithology showing coarser grain boundaries where recrystallization progressed further. Minor sulfide inclusions appear as small bright specks dispersed through both zones. No fusion crust remains on this interior slice.

Scientific context

Rumuruti chondrites represent fewer than 0.5% of all classified meteorites, making them among the rarest major chondrite groups. Unlike ordinary chondrites that formed in relatively reducing environments, R-chondrites crystallized under highly oxidizing conditions, producing their characteristic red-brown olivine and near-absence of metallic iron. The parent body remains unidentified, though spectroscopic studies suggest a main-belt asteroid with surface composition distinct from known ordinary, carbonaceous, or enstatite chondrite parent bodies. Thermal modeling indicates R-chondrite parent bodies underwent significant metamorphic heating, likely from radiogenic decay of short-lived isotopes like aluminum-26 in the early solar system.

Type 5-6 specimens like Sinawan 005 reached peak metamorphic temperatures between 750°C and 950°C, hot enough to homogenize olivine compositions and recrystallize chondrule mesostasis while preserving original chondrule outlines. The dual lithology in this specimen suggests either a breccia formed from fragments with different thermal histories, or a metamorphic gradient where the stone resided at a thermal boundary within its parent body. Learn About Meteorites provides additional background on chondrite classification and metamorphic processes.

Frequently asked questions

Is this meteorite authenticated? Yes. Sinawan 005 is classified as Rumuruti (R5-6) in the Meteoritical Bulletin following analysis of material recovered in 2023. The Meteoritical Bulletin entry can be accessed here: Sinawan 005. This specimen includes a certificate of authenticity from Treasure Coast Meteorite Co.

What does R5-6 classification mean? The R designation identifies this as a Rumuruti chondrite, a rare group characterized by high oxidation state and distinctive red-brown olivine. The 5-6 petrologic type indicates metamorphic heating to temperatures where olivine compositions homogenized and matrix recrystallized, but not hot enough to completely destroy chondrule textures. The dual number reflects transitional features between type 5 and type 6 metamorphic grades within this single stone.

What makes this specimen scientifically significant? Only three specimens of Sinawan 005 have been classified worldwide as of 2023. The dual lithology zones preserved in this slice represent heterogeneous metamorphic conditions rarely seen in individual R-chondrite stones. This specimen has been referenced in published scientific literature examining its unique structural features and formation history.

What is included with this specimen? The 17.32g slice and a certificate of authenticity. No display stand is included with this listing.

Collector significance for rare R-chondrites

Sinawan 005 offers collectors access to one of the rarest chondrite groups with an exceptionally limited total known weight distributed across only three classified specimens. The dual lithology visible in this slice provides a display feature that distinguishes it from typical single-zone R-chondrite slices. At 17.32g, this specimen represents substantial size for a material type where most available pieces measure under 10g due to extreme scarcity. The transitional R5-6 classification adds scientific interest, as most R-chondrites fall cleanly into a single metamorphic type rather than straddling grade boundaries.

R-chondrites remain significantly underrepresented in most meteorite collections compared to ordinary chondrites, making any classified specimen a priority acquisition for collectors building comprehensive type collections. This piece combines scientific importance, visual interest from the lithology contrast, and rarity as one of three known examples of its specific classification. Collectors focused on Chondrites will find few opportunities to acquire R-type material with this level of documentation and structural complexity.

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