Northwest Africa 11025 (NWA 11025)

(Northwest Africa)

Find: 2011

Classification: Ordinary chondrite (H3)

History: Purchased by Dustin Dickens 2011 from a mineral dealer in Midelt, Morocco.

Physical characteristics: Single stone with flat, cracking, partially oxidized fusion crust covering the entire stone

Petrography: (A. Rubin, UCLA) Average chondrule size is 300-400 μm, in the H-chondrite range. The olivine distribution has a large peak at Fa_17-18, within the H-chondrite range. The low average Fa value is due to a low-FeO tail in the distribution; the large standard deviations in olivine and pyroxene indicate that the rock is somewhat unequilibrated. Chondrules are very sharply defined, but chondrule glass is absent. However, there are shock features in the rock including irregular small troilite grains within metallic Fe-Ni grains, rare small grains of metallic Cu within metal grains and patches containing broken silicate fragments within troilite. This suggests that the rock has been shocked. Taken together with the sharp optical extinction of the olivine grains, it seems likely that the rock was shocked and then annealed. This is consistent with the paucity of polysynthetically twinned low-Ca monoclinic pyroxene grains.

Geochemistry: Mineral composition and geochemistry: olivine Fa_15.6±4.8 (n=14) low-Ca pyroxene Fs_14.9±3.7Wo_1.4±0.6 (n=12)

Classification: H3

Specimens: 47.5 g at UCLA, including a thin section.