Large pebble of hyalobasanite from St. Paul Island. Phenocrysts are yellow olivine (Fa20) making up about 5% of the rock with an occasional phenocryst of black augite. The groundmass consists of thin laths of labradorite, irregular grains of brownish augite, and small rounded grains and some skeletons of ore. Considerable colorless glass is present which has a refractive index of n=1.53-1.54. (Description from Barth, 1956)
Rocks of the Pribilof Islands
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