Medium light-fray (N6) olivine basalt flow. Vesicular, with seriate intersertal texture. Plagioclase crystals reach a maximum size of 1 mm and have a median composition of about An72. The outer rims and smaller crystals are oligoclase. The salite, which attains dimensions of 3 mm, and makes up about 6% of the rock has nZ 1.722 plus/minus 0.003, nY 1.698 plus/minus 0.003, and nX 1.688 plus/minus 0.003 suggesting a composition of Ca50Mg32Fe18. Olivine crystals attain a maximum size of 1 mm, are clove-brown, and have nX 1.694 and nZ 1.743, suggesting a composition of Fa30-34. Magnetite in rounded grains, as much as 1 mm across, is the principal accessory mineral. A few cumulophyric clots of magnetite, olivine, and clinopyroxene are present. A small amount of cloudy glass remains. Irregular vesicles are lined with tridymite.
Magmatic differentiation in Tertiary and Quaternary volcanic rocks from Adak and Kanaga Islands, Aleutian Islands, Alaska