rhyolite (riolit)

[Irreg. tinguished from it by the presence of quartz as an e ential ingredient, and also by a great variety of texture, showing more distinctly than rocks usually do that the material had flowed while in a viscous state. The name liparite was given later by J. Roth to rocks of similar character occurring on the Lipari Islands. Non-vitreous rocks of this kind had previously been called trachytic porphyries, and they have also been designated as quartz -trachytes. Later Richthofen proposed the name of nevadite (also called granitic rhyolite by Zirkel) for the variety in which large macroscopic ingredients, like quartz and sanidine, predominated over the ground-ma , retaining the name liparite, and applying it to the varieties having a porphyritic or felsitic structure, and limiting the term rhyolite to the lithoidal and hyaline modifications, such as obsidian, pumice-stone, and perlite; and nearly the same nomenclature was adopted by Zirkel. Rosenbusch recognizes as structural types of the rhyolitic rocks nevadite, lip arite proper, and gla y liparite, remarking that these names na correspond closely to Zirkel's nevadite, rhyolite, and gla y rhyolite respectively. These rocks are abun dant in various countries, especially in the Cordilleran region, and are interesting from their connection and a ociation with certain important metalliferous deposits. See cut under axiolite . rhyolitic (rī-ō-litik), a. [ rhyolite + -ic.] Composed of or related to rhyolite. Quart . Jour. Geol . Soc . , XLV. 198. rhyparographic (rip"a-rō-graf'ik), a . [ rhyp arograph-y+-ic.] Pertaining to or involved in rhyparography; dealing with commonplace or low subjects. She takes a sort of naturalist delight in describing the most sordid and shabbiest features of the least attractive kind of English middle-cla life, and in doing this never mi es a rhyparographic touch when she can introduce one. The Academy , April 3, 1886, p. 234.