A partially fusion-crusted stone weighing 1.9 kg was found in Morocco by a French team under the organization of Bruno Fectay and Carine Bidaut. NWA 1232 was classified at Kobe University (K. Tomeoka) as a CO3-group carbonaceous chondrite that contains two different lithologies—one dark gray and the other light gray, each containing slightly different modal amounts of chondrules, CAIs, and AOIs. Chondrules in the two lithologies also differ slightly in their size.
After further studies were conducted, Kiriishi and Tomeoka (2008) identified additional differences that exist between the two lithologies (Lith A and Lith B). One of these differences is a significant variation in the Fa content of chondrule olivine phenocrysts (Lith A: Fa4–15; Lith B: Fa20–40). A similar but reversed variation in fayalite content occurs in the olivine grains within the matrices of the respective lithologies, with Lith B also showing a more homogeneous composition (Lith A: Fa41–59; Lith B: Fa38–44). Another evident difference is a higher abundance of the secondary mineral nepheline in components of Lith B compared to those of Lith A. Each of these features indicate that Lith B experienced a higher degree of thermal metamorphism than Lith A. The disparate features in these two NWA 1232 lithologies probably reflect a brecciation process involving rocks which experienced different degrees of thermal metamorphism prior to their final mixing and lithification.
The specimen shown above is a 13.33 g partial slice that contains both lithologies. The photo below shows the main mass of this unusual meteorite.
Photo courtesy of B. Fectay and C. Bidaut—meteorite.fr
