| Text Description: |
Sample typical of East Cape volcanic rocks. Dense, medium gray rocks, with 80 to 90% of plagioclase, ranging in composition from An50 to An70; 10 to 15% of hornblende, which is brown, with a deep black resorption border and a low extinction angle; and about 1% of hypersthene. 2% of magnetite and a small amount of apatite, in cloudy prisms ranging in size from 0.2 to 0.02 mm, are also present. The groundmass is a very fine-grained unorientated aggregate of prisms of oxyhornblende, augite, laths of plagioclase, and grains of magnetite, with a little interstitial orthoclase. |
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