What phenocryst minerals would you expect to find in an aphanitic rhyolite flow?
A)quartz and K-feldspar
B)intermediate (Ca-Na)plagioclase and amphibole or pyroxene
C)Ca-rich plagioclase and olivine
D)apatite and muscovite

Question

Quizplus · Accepted Answer

Aphanitic rocks have small mineral grains that are not easily visible to the naked eye. Rhyolites are generally felsic rocks consisting of quartz, K-feldspar, and plagioclase. In aphanitic rhyolites, the mineral grains would be too small to see without magnification, but larger crystals (phenocrysts) of quartz and K-feldspar may be present.

What Phenocryst Minerals Would You Expect to Find in an Aphanitic