Northwest Africa 13758 meteorites were first recovered from the Algerian Sahara in 2017. A strewnfield near the town of Reggane on the Tanezrouft plateau yielded hundreds of small stones and fragments. Many of these specimens had exposed chondrules on the surface, hinting at an unequilibrated type. A sulphurous odor was detected during cutting, which is typically a signature of sulfur-rich types like Rumurutis and some carbonaceous meteorites. Specimens were sent to the University of New Mexico for analysis and Dr. Carl Agee classified this meteorite as a R3 Rumuruti type that shows two lithologies. The first lithology is slightly less equilibrated (R3.7) and the second lithology is more altered at R3.9.
The specimens being offered here are uncut fragments that are presented as-found in the desert. They have only had a light brushing to remove surface dust. These pieces could be windowed and polished to show a brecciated matrix packed with chondrules. This fragment weighs approx. 1.42 grams.
Refer to the photo. The black centimeter cube is shown for scale and is not included. You are purchasing the specimen shown. Your purchase will include a labeled gemjar for safe storage.
From the Meteoritical Bulletin entry on NWA 13758 :
Northwest Africa 13758 (NWA 13758)
Classification: Rumuruti chondrite (R3)
History: A large group of identically appearing stones, found together, was purchased by a Saharan dealer from a nomad in Algeria. The original find was reportedly in the Tanezrouft Plateau, with the nearest town being Reggane, Algeria.
Physical characteristics: Approximately 500 pieces ranging in mass from <1 kg to >5 kg, with a total known weight of approximately 100 kg. Dark brown sandblasted exterior. Saw cut reveals a breccia with fragments up to ~2 cm set in a fine-grained matrix. Abundant distinct chondrules are visible throughout. Two main lithologic domains exist within this meteorite, one has a gray, unstained matrix, and the second has a brownish-orange-stained matrix.
Petrography: (C. Agee, UNM) Chondrite with mean apparent chondrule size 350±240 µm (n=21) set in abundant matrix (~35 vol%). Electron microprobe analyses were performed separately on the two main lithologic domains. Domain "A" has compositionally unequilibrated olivine and pyroxene both in chondrules as well as single mineral fragments in the matrix. Very small grains of albitic plagioclase are present. Chromite, pentlandite, and troilite are ubiquitous. No metal or oxidized iron was detected. Domain "B" has compositionally unequilibrated olivine and pyroxene both in chondrules as well as single mineral fragments in the matrix. Domain "B" appears to have slightly more chondrules than domain "A". Very small grains of albitic plagioclase were present. Ti-rich chromite, pentlandite, and Ni-bearing troilite are ubiquitous. No metal or oxidized iron was detected.
Geochemistry: (C. Agee, UNM) Domain "A": olivine Fa36.6±8.4, CV=23%, Fe/Mn=83±15, n=12; low-Ca pyroxene Fs21.4±6.8Wo0.9±0.5, Fe/Mn=39±19, n=4; augite Fs8.8±0.7Wo46.0±0.2, Fe/Mn=43±4, n=2; plagioclase An8.8±0.6Ab86.5±0.2Or4.7±0.7, n=3. Domain "B": olivine Fa38.7±5.8, CV=15%, Fe/Mn=87±10, n=12; low-Ca pyroxene Fs10.0±7.7Wo2.0±1.8, Fe/Mn=15±7, n=4; augite Fs11.4±0.9Wo44.8±1.3, Fe/Mn=51±11, n=2; plagioclase An9.2±0.9Ab85.9±1.6Or4.9±0.8, n=3.
Classification: Rumuruti chondrite (R3). Domain "A" is approximately R3.7 and domain "B" is approximately R3.9, based on olivine coefficient of variation (CV) after Bischoff (2000).