| Text Description: |
Sample of an early flow from the northerly parasitic cone of Buldir Volcano. It is purplish gray, dense, and porphyritic, with a maximum grain size of 2 mm. Of the total volume, 35% is plagioclase phenocrysts, zoned, ranging in size from 2 to 0.5 mm, with a median composition of An60. 3% is olivine with a composition about Fa24. 2% is made up of augite and magnetite in the form of pseudomorphs after hornblende, and about 1% is hypersthene with a composition of about En60Fs40, judging from the negative 2V of about 60 degrees. Some hypersthene crystals have augite jackets. The groundmass, about 60% of the total volume, includes about 50% plagioclase, 3% hypersthene, 6% augite, and occasional prisms of cloudy apatite. The texture of the groundmass is also intergranular; between the plagioclase laths, ranging in length from 0.2 to 0.07 mm and in width from 0.02 to 0.08 mm, there are pyroxene granules from 0.04 to 0.01 mm in size and slightly smaller granules of magnetite. |
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