Definition of rhyolite in US English:



  • A pale fine-grained volcanic rock of granitic composition, typically porphyritic in texture.

    • ‘The conglomerate was deposited in tributary stream channels, and the pebbles consist almost entirely of quartz-feldspar phenocrystic rhyolite.’
    • ‘The age of the K-bentonite event is statistically indistinguishable from the age of the Chaschuil rhyolite.’
    • ‘Interesting specimens of rutile with bixbyite in rhyolite are reported from the vicinity of Marysvale, Utah.’
    • ‘The only thing that bothered me about the book was in vignette 18, describing Garnet Hill, where garnet crystals in rhyolite can still be collected.’
    • ‘A trail up the east side of the mountain, on public land, can still be taken, but collecting is now much more difficult in the limited amount of solid, unbroken rhyolite exposed on the summit.’


Mid 19th century: from German Rhyolit, from Greek rhuax ‘lava stream’ + lithos ‘stone’.