Northwest Africa 13520 (NWA 13520)

(Northwest Africa)

Purchased: 2008

Classification: Ordinary chondrite (L(H)3)

History: Purchased by Pat Brown in 2008 from an unknown NWA dealer in Tucson, Arizona.

Physical characteristics: Single partially crusted stone; fusion crust is light brown.

Petrography: (D. Sheikh, FSU) Sample is an ordinary chondrite composed of abundant chondrules (Av. 850±100 µm, n=30) set in a mostly opaque, slightly fine-grained matrix. Accessory phases include troilite and iron oxides.

Geochemistry: Olivine (Fa_16.9±6.4, range Fa_3.4-23.9, n=21), Cr₂O₃ in ferroan olivine (0.05±0.03 wt%, range <0.03 to 0.13, n=18) Low-Ca Pyroxene (Fs_9.4±5.4Wo_1.1±1.2, range Fs_1.2-17.6Wo_0.1-3.8, n=16).

Classification: Ordinary Chondrite (L(H)3) Cr₂O₃ in ferroan olivines is ~0.05 wt%, suggesting a high type 3 subtype (~3.8). While a few olivine grains are centered around Fa₂₃, suggesting an L group, the majority of them are FeO-poor compared to L3 chondrites. No olivine grains above Fa₂₄ were found. Likewise, no low-ca pyroxene grains were found above Fs_17. The observation of FeO-poor silicates relative to L3 chondrites leads to the L(H)3 classification.

Specimens: 28.98 grams at UCLA; main mass with Pat Brown.