| Text Description: |
Medium light-gray (N6) slightly vesicular hypocrystalline hypersthene andesite, with seriate texture. Larger plagioclase crystals, from 0.1 to 4 mm in size, range in composition from An77 to An55; most crystals are conspicuously zoned. The larger salite crystals, which attain a size of as much as 1 mm, are dark-greenish and have nZ 1.724, suggesting a composition of Ca50Mg27Fe22. The hypersthene, which is in euhedral prisms from 0.1 to 1 mm, has nZ 1.707, corresponding to a composition of En68Fe32. Magnetite, in irregular grains from 0.2 to 0.01 mm, and apatite, in stubby pseudodichroic prisms, are the principal accessory minerals. The groundmass consists of laths of oligoclase (median composition An23) and needles of pyroxenes, in a mosaic of orthoclase (?) and a clear glass with an index of 1.495 plus/minus 0.003. |