Biduna Blowhole 001        31°01’S, 131°19’E

South Australia, Australia

Found: 5 Dec 2009

Classification: Ordinary chondrite (L4)

History: The first piece was found on the Nullarbor Plain by A. Langendam. A further 16 fragments were located within a 30 m radius of the initial find.

Physical characteristics: Combined weight of all 17 pieces is 103.4 g, with the largest piece measuring 5 x 4 x 1 cm. The weathered surface is dark brown to black with small patches of orange lichens. Several pieces fit together like a jigsaw.

Petrography: (Kim Lai N. Bell, Monash) Main mass contains up to 65% chondrules within a dark, heavily rusted matrix. Mineralogy consists of olivine, pyroxene, minor plagioclase, Fe-Ni metal and sulfides. The dominant minerals, olivine and pyroxene, are mostly found in chondrules, with smaller grains (<50 µm) in the matrix. Plagioclase occurs in minor amounts and rarely exceeds 50 μm. Chondrules lack glass, are easy to discern and sometimes rimmed by sulfides or olivine. Chondrule types include RP, POP, GOP, PO and BO, with sizes ranging 0.1-2 mm and averaging 0.4 mm. Olivine and pyroxene grains display irregular to undulose extinctions, with larger grains containing planar fracturing. Up to 97% of all Fe-Ni metals and troilite are replaced by oxides.

Geochemistry: EMPA (wt%) Olivine: SiO₂ = 38.25, TiO₂ = 0.02, Al₂O₃ = 0.02, FeO = 24.94, MnO = 0.45, MgO = 37.47, CaO = 0.05, Na₂O = 0.01, K₂O = 0.01, (Fa = 25.6 mol%, σ = 2.5, n = 6). Low-Ca Pyroxene: SiO₂ = 56.34, TiO₂ = 0.10, Al₂O₃ = 0.21, FeO = 14.17, MnO = 0.44 MgO = 28.38, CaO = 0.40, Na₂O = 0.03, K₂O = 0.01, (Fs = 21.44 mol%, σ = 2.0, n = 6). Kamacite: Ni = 5.59, Co = 0.58. Troilite: Fe = 61.98, Ni = 0.10. Fe-Ni sulfide: Fe = 56.85, Ni = 1.33.

Classification: Ordinary chondrite (L5, S3, W4).

Specimens: All samples and one thin section are held by A. Tomkins at Monash.