A single stone weighing 668 g was found in Northwest Africa and later sold to a collector. A sample was submitted for analysis to Northern Arizona University (T. Bunch and J. Wittke), and NWA 2974 was classified as a CO3.1 carbonaceous chondrite, one of only a few rare CO chondrites recently determined to have this subtype. Northwest Afica 2974 has a shock level of S2 and a weathering grade of W2.
To discriminate among subtypes below type 3.2, it has been shown that the Cr content of ferroan olivine is an excellent indicator of metamprphism. Chromite exsolves from olivine in the incipient stages of metamorphism, initially producing heterogeneous Cr2O3 contents, and eventually low-Cr olivine. In a study by Chizmadia and Bendersky (2006), they determined that this sequence progresses from type 3.0, corresponding to high Cr2O3 contents of 0.3–0.4 wt%, to type 3.2, in which Cr2O3 constitutes less than 0.1 wt%. The gap between these subtypes representing type 3.1 was recently filled by the meteorites A-881632 (0.2–0.3 wt%), DOM 03238 (0.27 ±0.18), NWA 2718 (0.26 ±0.10), NWA 2760 (0.22 ±0.14), and NWA 2974 (0.11–0.53 wt%). The photo of NWA 2974 shown above is a 1.29 g partial slice.
