Sinawan 005 Rumuruti Meteorite Slice, R5-6, 20.29g, Dual Lithology Zones

Dual lithology zones define this complete slice

This complete slice of Sinawan 005 presents a stark visual contrast between light and dark lithology zones that divide the specimen face. The boundary between these zones cuts diagonally across the slice, creating a natural division that records two distinct formation episodes or thermal histories within the same meteorite. The lighter zone shows typical R-chondrite mineralogy with oxidized silicates, while the darker zone exhibits a different matrix composition and grain size distribution. This dual character appears throughout the 20.29g slice, making the structural variation immediately apparent.

The R5-6 classification indicates an intermediate metamorphic grade between type 5 and type 6, placing this specimen at a thermal threshold where chondrules remain visible but matrix recrystallization has begun. In Rumuruti chondrites, this grade produces especially clear textural boundaries when multiple lithologies are present. The slice preserves both zones completely, offering a cross-sectional view of the internal structure that formed in the parent body regolith.

Chondrule preservation and matrix structure

The lighter lithology zone retains well-defined chondrule outlines with diameters ranging from submillimeter to approximately 1.5mm. Matrix material between chondrules shows the fine-grained, oxidized character typical of Rumuruti meteorites, with reddish-brown coloration from iron oxide phases. Metal grains appear sparse and small, consistent with the highly oxidized nature of R-chondrites where metallic iron is largely absent compared to ordinary chondrites.

The darker zone displays tighter packing of mineral grains with less distinct chondrule boundaries, suggesting more advanced thermal metamorphism or a different original lithology. The textural contrast between zones provides direct evidence of regolith mixing on the Rumuruti parent body, where materials from different depths or locations were combined through impact processes before lithification. Surface weathering remains minimal, with fresh internal structure visible across both lithologies.

Scientific context

Rumuruti chondrites represent material from a parent body distinct from those that produced ordinary chondrites, carbonaceous chondrites, or enstatite chondrites. The R-chondrite group comprises less than 0.5% of all classified meteorites, making any specimen scientifically valuable. The oxidized mineralogy, low metal content, and oxygen isotope composition of Rumurutiites point to formation under conditions more oxidizing than those experienced by ordinary chondrites, likely in the outer asteroid belt.

Sinawan 005 holds additional significance as one of only three specimens classified at the R5-6 grade. This intermediate metamorphic state preserves information about thermal processing on the parent body while maintaining enough primary texture to identify original components. The dual lithology structure indicates regolith breccia formation, where surface materials were mixed by impacts and subsequently lithified. Learn About Meteorites for broader context on chondrite classification and parent body processes.

Frequently asked questions

Is this meteorite authenticated? Sinawan 005 is classified in the Meteoritical Bulletin as Rumuruti (R5-6), confirmed through thin section analysis and chemical characterization. The Meteoritical Bulletin entry documents the classification. This specimen includes a certificate of authenticity with the documented weight and classification.

What does R5-6 mean? The R designates Rumuruti-type chondrite, a rare group with oxidized mineralogy. The 5-6 indicates metamorphic grade between type 5 (chondrules distinct with recrystallized matrix) and type 6 (chondrules less distinct, extensive matrix recrystallization). This intermediate grade captures a specific thermal state on the parent body.

What is included with this specimen? The 20.29g complete slice and a certificate of authenticity documenting the classification and weight. No display stand is included.

What causes the dual lithology structure? The light and dark zones formed from separate materials that were mixed in the parent body regolith through impact processes. Different thermal histories or original compositions created the textural and color contrast. The zones were combined before the final lithification event that created the meteorite we see today.

How rare is this specific specimen? Sinawan 005 is one of three classified specimens at the R5-6 grade. Within the already rare Rumuruti group (less than 0.5% of all meteorites), specimens showing this clear dual lithology structure and complete preservation are exceptionally limited in availability.

Rarity drives collector interest in Rumuruti specimens

Collectors pursue Rumuruti chondrites because of their scarcity in the meteorite population and their distinct formation environment. With fewer than 100 classified R-chondrites worldwide, any specimen represents a fraction of available material. The R5-6 metamorphic grade exists at the boundary where primary textures meet thermal alteration, making these specimens valuable for understanding parent body thermal evolution.

This 20.29g complete slice offers display-ready dimensions with scientifically significant dual lithology structure visible across the entire face. The size provides enough mass to appreciate the textural contrast while remaining accessible for private collections. Complete slices with preserved boundaries between lithology zones are less common than fragments, as cutting typically separates zones rather than presenting them together. Explore additional rare chondrite specimens in our Chondrites collection.

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