Sinawan 005 Rumuruti Meteorite Slice, R5-6, 22.16g, Dual Lithology Zones

Dual lithology specimen from one of Earth's rarest meteorite groups

This 22.16g slice of Sinawan 005 preserves two distinct lithological zones in a single stone -- light and dark regions recording different stages of parent body metamorphism. The boundary between these zones runs diagonally across the face, creating a visual record of the complex thermal and impact history that characterizes R5-6 chondrites. Partial fusion crust along one edge marks its atmospheric entry path over Libya in 2023.

The dual lithology structure suggests either brecciation from impact events on the parent body, or variable metamorphic grades within a single host rock. Both zones show the oxidized mineralogy typical of Rumuruti chondrites -- high olivine content with elevated ferrous iron compared to ordinary chondrites. This specimen represents the complete slice, preserving the full transition between lithological domains.

Structure and features

The lighter lithological zone occupies roughly 60% of the face and displays a finer-grained matrix with scattered chondrule relicts, consistent with the type 6 metamorphic grade. The darker zone shows coarser crystallization and more pronounced grain boundaries, reflecting thermal processing at the type 5 boundary. Where the two zones meet, no sharp contact exists -- the transition occurs over several millimeters, suggesting gradational metamorphic conditions rather than mechanical mixing.

Small rounded chondrules remain visible in both zones despite the moderate to high metamorphic grade. These range from 0.3 to 1.2 millimeters in diameter and appear as subtle textural variations against the surrounding matrix. The fusion crust displays the characteristic black glassy surface formed during atmospheric deceleration, with flow lines indicating the stone's orientation during flight.

Scientific context

Rumuruti chondrites constitute less than 0.5% of all classified meteorites, making them among the rarest chondrite groups in collections worldwide. Their parent body remains unidentified, though spectroscopic studies have attempted to link R-chondrites to several near-Earth asteroids without definitive confirmation. The group takes its name from the Rumuruti meteorite that fell in Kenya in 1934, establishing the classification for this distinct oxidized chondrite family.

The R5-6 designation indicates metamorphic conditions near the transition between type 5 (where chondrules are still clearly defined) and type 6 (where chondrule boundaries become obscured by recrystallization). Only three specimens of Sinawan 005 have been classified and distributed globally, with this stone representing one complete slice from the original recovered mass. Learn About Meteorites provides additional context for understanding chondrite classifications and metamorphic grades.

Frequently asked questions

Is this meteorite authenticated? Yes. Sinawan 005 is classified in the Meteoritical Bulletin as Rumuruti (R5-6). You can verify this classification at Sinawan 005. This specimen includes a certificate of authenticity from Treasure Coast Meteorite Co.

What does dual lithology mean in this context? Dual lithology refers to the presence of two distinct textural and compositional zones within a single meteorite. In Sinawan 005, these zones likely formed from different metamorphic conditions on the parent body or represent fragments that were mechanically mixed during an impact event and later lithified together.

What makes Rumuruti chondrites chemically distinct? R-chondrites contain olivine with significantly higher FeO content than ordinary chondrites -- typically 38-40 mole percent fayalite. They also show higher bulk oxygen content and different oxygen isotope ratios, placing them on a separate formation path from H, L, and LL ordinary chondrites.

What is included with this specimen? The listing includes the 22.16g slice and a certificate of authenticity. No display stand is provided.

How rare is a type R5-6 specimen? Extremely rare. Only three classified specimens of Sinawan 005 exist worldwide. Rumuruti chondrites as a group represent less than half of one percent of all meteorite falls and finds, and those showing dual lithologies are scarcer still.

Collector significance

Sinawan 005 offers access to one of meteorite science's most underrepresented groups. With only three known specimens in existence, this slice provides a tangible connection to a parent body that remains astronomically unidentified. The dual lithology structure adds visual and scientific interest beyond what typical Rumuruti specimens display, making this piece notable even among R-chondrites.

The 22.16g mass provides sufficient size for display while representing a complete cross-section through both lithological domains. Collectors focused on rarity metrics or completing representative samples across all chondrite groups will find few opportunities to acquire classified R5-6 material. This specimen bridges the gap between type 5 and type 6 metamorphic grades, documenting thermal evolution on a parent body that delivered less than 200 classified specimens to Earth across all recorded history. Browse additional rare chondrite classifications in our Chondrites collection.

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