Northwest Africa 16411 . Purchased: 2023 May Classification: Ureilite Petrography: (K. Metzler, IfP) Coarse-grained ultramafic rock, consisting of olivine and pyroxene grains with sizes up to several mm. Reduction features in olivine, i. e., reverse zoning and occurrence of tiny Ni-free metals at the margins, along cracks, and within the grains. Graphite occurs along silicate grain boundaries. Most metal has been oxidized by terrestrial weathering. Geochemistry: Mineral compositions and geochemistry: Olivine core composition: Fa22.1±0.3 (Fa21.7-22.4; n=6); Fe/Mn (at.): 42.4. CaO concentration in olivine: 0.2 wt%. Reduction zones in olivine: Fa3.4±0.2 (Fa3.1-3.6; n=5); Fe/Mn (at.): 7.5. Pyroxene composition: Fs18.6±0.2Wo9.2±0.2 (Fs18.2-18.9Wo9.0-9.5); n=8. The mean concentration of Cr2O3 (wt%) in olivine and pyroxene is 0.4 and 1.2, respectively. Classification: Ureilite, based on modal composition, mineral chemistry, occurrence of considerable amounts of graphite, and typical reduction features in olivine. Shock stage: U-S2 Weathering grade: Strong Classifier: K. Metzler, IfP This lot comes with certificate of authenticity. Thanks for your interest.