Sinawan 005 Rumuruti Meteorite Slice, R5-6, 24.45g, Dual Lithology Zones

Two lithologies in a single slice

This Sinawan 005 specimen preserves two distinct lithologies within one slice. A light-toned zone and a darker zone meet at a sharp contact, representing different thermal or shock histories within the same parent body. The boundary between these regions cuts cleanly across the face, making the structural division immediately visible. At 24.45g, this slice captures the full width of both zones in a single cross-section. Fusion crust fragments remain along portions of the edge, marking the original exterior surface of the meteorite.

Sinawan 005 is classified as R5-6, placing it at the thermal transition between type 5 and type 6 petrologic grades. This dual grading reflects heterogeneous heating within the Rumuruti parent body. The light zone shows characteristics of higher metamorphic grade, while the darker zone retains features of lower grade material. Both zones coexist because the parent body experienced uneven internal heating, possibly from impact or radioactive decay in localized regions.

Structure and features

The contact zone between the two lithologies is the defining structural feature. This boundary is not gradational but abrupt, suggesting that the two regions formed under different conditions and were later juxtaposed, likely through impact brecciation. Chondrule outlines are visible in both zones, though better preserved in the darker material. The lighter zone displays more recrystallized matrix, consistent with higher metamorphic alteration. Small metal grains are distributed throughout both lithologies, appearing as bright flecks against the silicate background.

The slice surface shows natural texture without artificial polish. This preserves the native contrast between the two zones and allows direct observation of the mineralogical differences. Fusion crust, where present, is thin and dark, typical of Rumuruti chondrites, which produce less pronounced crusts than ordinary chondrites due to their oxidized composition.

Scientific context

Rumuruti chondrites represent approximately 0.5% of all classified meteorites, making them one of the rarest major chondrite groups. They are named after the Rumuruti meteorite, which fell in Kenya in 1934. R chondrites are oxygen-isotope distinct from ordinary, carbonaceous, and enstatite chondrites, indicating they originate from a separate parent body. That body remains unidentified, though it likely resides in the inner asteroid belt based on orbital dynamics.

The R5-6 classification indicates that this meteorite experienced peak metamorphic temperatures between approximately 700°C and 950°C. This heating caused recrystallization of matrix minerals and partial equilibration of olivine and pyroxene compositions. The dual lithology structure suggests that different regions of the parent body reached different peak temperatures or cooled at different rates. Impact mixing later brought these zones together into a single rock. Learn About Meteorites to understand how petrologic types reflect thermal history.

Frequently asked questions

Is this meteorite authenticated? Sinawan 005 is classified in the Meteoritical Bulletin as Rumuruti (R5-6), found in Libya in 2023. The full classification details are available through the Meteoritical Bulletin database. This specimen includes a certificate of authenticity documenting its provenance and classification.

What does dual lithology mean in this context? Dual lithology refers to two distinct rock types present in the same specimen. In this slice, one zone shows higher metamorphic grade (lighter color, more recrystallization) while the other shows lower grade (darker, better-preserved chondrules). The sharp boundary between them indicates they were brought together by impact processes on the parent body, not by gradual transition.

What is included with this specimen? The specimen weighs 24.45g and includes a certificate of authenticity. No display stand is included.

Why is the R5-6 designation significant? The hyphenated grade (R5-6) indicates that this meteorite contains characteristics of both petrologic type 5 and type 6. This intermediate classification is less common than single-type assignments and reflects thermal heterogeneity within the parent body. It places the specimen at a key transition point in metamorphic evolution.

How rare is Sinawan 005 specifically? Only three specimens of Sinawan 005 have been classified and documented. This makes it exceptionally scarce even within the already-rare Rumuruti group. The meteorite has been the subject of published scientific research due to its unusual dual lithology structure.

Scientific importance and collector positioning

Sinawan 005 is one of three known specimens at this specific classification, making it scientifically significant beyond the inherent rarity of R chondrites. The dual lithology structure has been documented in peer-reviewed literature, confirming that this meteorite preserves direct evidence of thermal and impact processes on the Rumuruti parent body. Collectors seeking scientifically noteworthy specimens will find few opportunities more compelling than a meteorite with published research and documented scarcity at this level.

The slice format allows full observation of both lithologies in their natural contact relationship. This is not a polished display piece but a research-grade cross-section that reveals internal structure. The 24.45g size is substantial enough to show both zones completely while remaining accessible for private collections. Chondrites of this rarity and documented significance rarely appear on the collector market. This is one of three chances to own this specific find.

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