Ifould Lake 001        30°51’S, 132°05’E

South Australia, Australia

Found: 24 Aug 2008

Classification: Ordinary chondrite (L5)

History: A solitary piece was found lying on the stony surface of the Nullarbor Plain by K.L. Bell.

Physical characteristics: The sub-rounded, pyramidal-shaped stone weighs 40.9 g and measures 3.5 cm on the longest axis. The exterior is dark reddish brown, with the exception of darker, remnant fusion crust (~10%) and several paler colored macro-chondrules, up to 5 mm. The interior is dark brown to black and shows chondrules and metallic specks.

Petrography: (Kim Lai N. Bell, Monash). Chondrules and chondrule fragments lie within a fine-grained recrystallized matrix cross cut by dark μm to mm thick veins. Mineralogy consists of olivine, pyroxene, plagioclase, sulfides, Fe-Ni metal and minor ringwoodite, maskylenite and chromite. Olivine displays undulose to mosaic extinction, and larger grains contain PDFs. Pyroxene grains also exhibit similar textures. Plagioclase generally >50 μm, with some grains replaced by maskylenite. Troilite (~10%) and Fe-Ni metal (3%) occur as irregularly shaped grains, with up to 35% replaced by oxides. Chondrules 0.3 to 5 mm, mean ~0.6 mm, with some more readily discernable than others due to recrystallization. Textural types include BO, POP, GOP, PP, RP, PO, and PP. An Al-rich chondrule containing maskylenite, olivine and very fine-grained chromite was observed.

Geochemistry: EMPA (wt%) Olivine: SiO₂ = 37.55, TiO₂ = 0.01, Al₂O₃ = 0.03, FeO = 23.32, MnO = 0.47, MgO = 38.52, CaO = 0.02, Na₂O = 0.01, K₂O = 0.01, (Fa = 25.35 mol%, σ = 0.79, n = 11). Low-Ca pyroxene: SiO₂ = 54.24, TiO₂ = 0.18, Al₂O₃ = 0.27, FeO = 14.37, MnO = 0.45, MgO = 28.59, CaO = 0.64, Na₂O = 0.03, K₂O = 0.01, (Fs = 21.72 mol%, σ = 0.73, n = 2). Plagioclase: SiO₂ = 71.14, TiO₂ = 0.05, Al₂O₃ = 22.94, FeO = 0.24, MnO = 0.01, MgO = 0.01, CaO = 2.30, Na₂O = 2.60, K₂O = 1.08 (An = 28.95, σ=1.84, n = 5). Kamacite: Ni = 6.39, Co = 0.89. Troilite: Fe = 62.96, Ni = 0.10. Pentlandite: Ni = 8.49, Co = 0.34.

Classification: Ordinary chondrite (L5, S5, W2).

Specimens: A single specimen plus one polished thin section are held by A. Tomkins at Monash.