| Text Description: |
Sample from the main cone. Holocrystalline purplish, somewhat porous rock, with a maximum grain size of 1.5 mm. It consists of about 70% plagioclase, from An70, to An50 in composition, with a median of about An62; about 5% olivine (Fa15), 20% augite, 3% magnetite, and 2% of pseudomorphs of magnetite and augite after hornblende. The texture is intergranular and essentially seriate, as no well-defined break in range of grain sizes is present. The smaller grains of augite, ranging in size from 0.1 to 0.04 mm, are, together with magnetite, interstitial to the somewhat lath-like crystals of plagioclase. The olivine shows a slight color zoning, the outer part having a higher index and slightly darker color, presumably reflecting a higher content of iron. |
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