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Compact, holocrystalline, pale-red (5R 5/1) olivine basalt with seriate texture. About 60 per cent of crystals of plagioclase are from 2 to 0.2 mm in diameter and range in composition from An84 to An31, with a median of about An72. The augite crystals, which reach a maximum size of 3 mm and make up about 5% of the rock, are olive-black (5Y 2/1) in hand specimen. The maximum index is about 1.72 and the intermediate index about 1.70, suggesting a composition near Ca50Mg30Fe20. The olivine is dark yellowish-orange in hand specimen (10YR 6/6) and the largest grains are about 0.5 mm across. The indices determined are nX 1.688 plus/minus 0.002 and nZ 1.726 plus/minus 0.003, indicating a composition of about Fa28. The principal accessories are magnetite and ilmenite in grains from 0.5 to 0.2 mm; the groundmass consists of blocky plagioclase crystals, augite granules, magnetite, and interstitial orthoclase. |