Northwest Africa 10058 (NWA 10058)

Morocco

Purchased: 2014

Classification: Ordinary chondrite (H3)

Petrography: The average kamacite Co content is 0.52 wt.%, consistent with H. Chondrules average about 300 μm in diameter, consistent with H. The Cr₂O₃ content of ferroan olivine grains (n=18) is 0.06±0.08 The rock contains a dark-colored clast, which is poorer in coarse metal and sulfide than the chondritic host. There are curvilinear trails of metal and sulfide dispersed through the clast, indicating shock darkening. Many of the low-Ca pyroxene grains exhibit polysynthetic twinning. Chondrules do not contain clear, isotropic glass.

Geochemistry: Olivine Fa_12.9±7.6 (n=20) and pyroxene Fs_8.3±6.3Wo_0.7±0.5 (n=18)

Classification: The sharply defined chondrules, presence of recrystallized silicate matrix material, and absence of Coarse chromite and plagioclase grains indicate that it is petrologic type 3. The olivines are compositionally more heterogeneous than those in H3.8 Dhajala, indicating that the petrologic type is <3.8. The absence of clear, transparent isotropic glassy mesostasis in the chondrules is characteristic of subtype 3.6-3.9. Most of the low-Ca pyroxene phenocrysts in chondrules exhibit polysynthetic twinning, indicative of subtype =<4. According to Table 1 of Huss et al. (2006), this is consistent with subtype =<3.4. Low-Ca pyroxene is also heterogeneous with a PMD of 62.9%, consistent with subtype =<3.6. The Cr₂O₃ data in ferroan olivine is indicative of subtype =>3.2. The analytical data suggest subtype 3.4 or so, but from the absence of clear isotropic mesostasis, the higher range is a better classification as H3.6.