1. rhyolite

noun. very acid volcanic rock.

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Example sentences of the word rhyolite

1. Noun, singular or mass
Breaking or prying open the crevasses of rhyolite, a white to dark gray rock found in the area, reveals the crystals.

2. Adjective
These are volcanic geodes, which have igneous rhyolite rinds rather than the sedimentary limestone or dolomite of the Midwest.