NWA 11755 Ureilite
Northwest Africa 11755 (NWA 11755)
Purchased: 2017 Sep
Petrography: (K. Metzler, IfP) Coarse-grained ultramafic rock with metamorphic texture (~120° triple junctions), consisting of olivine and pyroxene grains up to ~5 mm. Reverse zoning of olivine grains with Mg-rich zones at the margins and along cracks. Graphite and partly oxidized metal are concentrated along grain boundaries.
Geochemistry: Mineral compositions and geochemistry: Olivine cores (n=12): Fa21.3±0.3; Olivine rims (n=5): Fa9.0±2.0. Pyroxene grains (n=13): Fs11.8±1.5Wo6.1±1.8. The Cr2O3 concentration in olivine and pyroxene is 0.7 wt% and 1.0 wt%, respectively.