Noun
English Wikipedia has an article on:rhyodaciteWikipedia
rhyodacite (countable and uncountable, plural rhyodacites)
(geology) An extrusive volcanic rock intermediate in composition between dacite and rhyolite
Volcanic activity became concentrated in the vicinity of the present site of Long Valley Caldera 3.1 to 2.5 million years ago with eruptions of rhyodacite followed by high-silica rhyolite from 2.1 to 0.8 million years ago. Source: Internet
Mammoth Mountain is a lava dome complex in the southwestern corner of the caldera, consisting of about 12 rhyodacite and dacite overlapping domes. Source: Internet