| Text Description: |
Sample of the dome on the flank of East Cape Volcano. This sample is hypersthene-bearing hornblende basalt, pale gray, porous in structure, with a faint lineation due to the orientation of the hornblende prisms. About 4/5 of the coarser part of the rock consists of plagioclase grains from 0.02 to 0.6 mm in size, with an average composition of An55. Hornblende, about 10% by volume, is greenish brown, and the needles are from 0.02 to 2 mm long. The hypersthene prisms, which form about 3 % of the rock, are from 0.02 to 0.4 mm in length. Magnetite grains make up about 2% and augite about 1% of the rock. Traces of apatite, olivine (Fa18), and glass (n=1.515) are present. A small amount of analcime(?) appears to replace both glass and plagioclase. The groundmass, which forms about 20% of the whole rock, consists of unoriented augite needles, averaging about 0.0002 by 0.02 mm in size, plagioclase crystals, 0.01 by 0.02 mm, and magnetite granules, in glass. |
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