rhyodaciten.
/rʌɪəˈdeɪsʌɪt/, U.S. /ˌraɪəˈdeɪˌsaɪt/ Geology.
A relatively light-coloured, extrusive volcanic rock with a fine-grained porphyritic texture, intermediate in composition between rhyolite and dacite.
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the world > the earth > structure of the earth > constituent materials > rock > igneous rock > [noun] > porphyrite rock > varieties of
red rock1721
oriental verd-antique1852
kersanton1862
kersantite1868
uralite-porphyry1868
monchiquite1891
vogesite1891
camptonite1895
hedrumite1896
wyomingite1897
spessartite1908
rhyodacite1913
rhyolite1932
1913 A. N. Winchell in Jrnl. Geol. (Chicago) 21 214 The volcanic equivalent of granodiorite, which may be appropriately called rhyodacite, forms another intermediate group between the alkalcic and the alkaline rocks.
1932 A. Johannsen Descr. Petrogr. Igneous Rocks II. 356 Rhyodacites..are rocks of porphyritic habit, usually white, yellowish, reddish, or grayish in colour, and showing phenocrysts of quartz, plagioclase, and some ferromagnesian constituent, in a microcrystalline, cryptocrystalline, or glassy ground~mass.
1977 A. Hallam Planet Earth 164/1 Most provinces of rhyolitic volcanics contain substantial amounts of rhyodacite as well as true rhyolite.
2004 Amer. Antiq. 69 122/1 The tools were replicated from volcanic (rhyodacite) beach cobbles available near the site.
This entry has been updated (OED Third Edition, June 2010; most recently modified version published online March 2022).
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n.1913