rhyolite noun. ['rʌɪǝlʌɪt] M19.
[Irreg. from Greek rhuax stream (of lava) + -LITE.]
Geology. Orig., a variety of trachyte containing quartz; later, any volcanic rock showing a fluidal texture. Now, an acidic extrusive volcanic rock, usu. pale and of porphyritic texture, with phenocrysts esp. of quartz or potassium-feldspar in a fine-grained or glassy groundmass commonly showing fluidal structure.

■ rhyodacite [rʌɪǝ'deɪsʌɪt] noun a porphyritic igneous rock intermediate in composition between rhyolite and dacite E20.

■ rhyolitic [-'lɪtɪk] adjective pertaining to, resembling, or related to rhyolite M19.

[TahlilGaran] English Dictionary ▲