Northwest Africa 11549 (NWA 11549)

(Northwest Africa)

Purchased: 2013

Classification: HED achondrite (Eucrite)

History: Donated to Cascadia by Mr. John A. Shea, who purchased the sample in 2013 from Mr. Steve Witt who in turn had acquired the specimen in a lot of NWA meteorites from an unknown trader.

Physical characteristics: Remnant fusion crust and broken surfaces with light orange weathering patina visible on two pieces. Cut surfaces reveal light-gray interior with minimal weathering staining, including coarser portions and finer portions. Coarser areas are dominated by grey pyroxene and lighter colored plagioclase up to ~1 mm across

Petrography: Contains clasts rich in plagioclase and pyroxene with textures that range from ophitic to subpohitic to granular. Pyroxene grains sometimes show micron-scale exsolution lamellae. Minor weathering product.

Geochemistry: Bulk pigeonite Fs_55.1±5.8Wo_12.0±6.7, taken as average of all pyroxene with Wo_5.5-35 (N=150), low-Ca pyroxene in fusion crust Fs_48.4±3.0Wo_4.3±0.6 (N=4); augite Fs_37.1Wo_35.3 (N=1); plagioclase An_85.2±2.3Ab_14.4±2.0 (N=91). Fusion crust glass (average of 14 analyses, wt. %): SiO₂ 47.4±0.6, TiO₂ 1.0±0.2, Al₂O₃ 11.0±0.3, Cr₂O₃ 0.25, FeO 20.6±0.4, MnO 0.69±0.1, MgO 6.8±0.1, CaO 9.9±0.4, Na₂O 0.53±0.04, total 98.1±0.7.

Classification: Monomict eucrite based on texture and mineral composition. Composition of fusion crust glass, proxy for bulk rock composition, is similar to non-cumulate eucrites such as Juvinas

Specimens: Cascadia holds 2 pieces (5.7 g, 1.7 g), a polished thin section, and a potted butt. Mr. John A. Shea (201 East Rose Valley Rd, Wallingford PA, 19086) holds the main mass