rhyolite


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rhyolite,

fine-grained light-colored acidic volcanic rockrock,
aggregation of solid matter composed of one or more of the minerals forming the earth's crust. The scientific study of rocks is called petrology. Rocks are commonly divided, according to their origin, into three major classes—igneous, sedimentary, and metamorphic.
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. Rhyolite is chemically the equivalent of granite, and is thus composed primarily of quartz and orthoclase feldspar with subordinate amounts of plagioclase feldspar, biotite mica, amphiboles, and pyroxenes. Rhyolite lava exhibits a typical banded structure produced by its flow pattern. Rhyolite lavas occur in continental and submarine volcanoes, especially island arcs, and in igneous dikes. Rhyolite lavas are typically highly viscous and are explosively ejected from volcanoes. Rhyolites were formed in profusion in the Yellowstone Park area and throughout the southwestern portion of the United States.

Rhyolite

 

(also liparite), a cenotypal, extrusive rock rich in silica (68-77 percent SiO2). It has a porphyritic texture and contains phenocrysts of quartz, potassium feldspar, plagioclase, and, less commonly, biotite or pyroxene in a glassy groundmass, usually with flow texture. A glassy variety virtually without phenocrysts is called obsidian. Paleotypal analogs are classified according to their alkali composition as keratophyres (sodic) or orthophyres (potassic). Rhyolite is the extrusive equivalent of granitoids.

rhyolite

[′rī·ə‚līt]
(petrology)
A light-colored, aphanitic volcanic rock composed largely of alkali feldspar and free silica with minor amounts of mafic minerals; the extrusive equivalent of granite.
References in periodicals archive ?
* PC19-09 returned several wide intercepts of gold mineralization within rhyolite extending gold mineralization 25m to the northwest of PC18-28, which intersected 48.77m of 0.64 g/t Au (see news release September 20, 2018)
6b) is very thin, triangular in outline, and lenticular in cross-section, extensively but irregularly flaked on Group A rhyolite. Lateral margins are slightly convex and asymmetrical.
Me quede asombrado, tanto como cuando las encontre cerca de Rhyolite, en el camino de Cane Springs, al ver lo nuevas que parecian.
Rhyolite, a natural volcano stone pumice in both course and fine grinds, and other ingredients in Xtend-Life's Age Defying Exfoliating Scrub, will help Dad: refine skin texture, clean clogged pores, prevent blackheads, moisturize below the skin's surface, support skin health and its ability to resist bacteria, boost the skin's defense system, restore and maintain the skin's protective barrier, and more.
A fact highlighted by different authors is the presence of up to 60 % of igneous clasts in the conglomerates of this formation (Quartino et al., 1971; De Rosa, 1983; Tofalo et al., 1985; Sessarego et al., 1990), including granites, quartz monzonites, quartz syenites, syenites, rhyolites, rhyodacites and basaltic rocks (Sessarego et al., 1990).
(1991) and Richerson (1990) refer to two separate periods of volcanism; rocks belonging to the "young group" are less than 5 Ma and tend to be dacites; and the "old group" which "consists of basalts and basaltic andesites as well as andesites to rhyolites" (Richerson, 1990).
Originally empty, the excavated space has filled with debris fallen from the slowly eroding interior walls, an exposed stratified frieze of sandstone and rhyolite. Both matters have microstructures that are porous and quivering with potential for transformation.
One of the main rock groups encountered at this site is composed of igneous rocks such as granite, granodiorite, dolerite, basalt and rhyolite. Almost no data pertaining to engineering properties of these rocks is available in public domain in Pakistan.
Rhyolite 2.30 Lingfield SP forecast 5-4 Showed little in three 7f-1m1/2f maidens last year but attracted support on his return from a break in a 7f handicap at Wolverhampton 12 days ago and was beaten a length into second, splitting two previous winners.
MOSCROP'S TREBLE Polar Venture (nap) 3.05, Lingfield Rhyolite 2.30, Lingfield Experimentalist 6.00, Wolverhampton TODAY'S SARABAND SELECTIONS KEMPTON: 1.45 Ericht, 2.15 Pearl Swan, 2.50 Salden Licht (nap), 3.25 Moonlight Drive, 3.55 Spoil Me, 4.25 Peintre Star, 4.55 Dr Livingstone.
NAOMI MATTHEW: 1.00 Princess Cammie, 1.30 Beach Candy, 2.00 Azrael, 2.30 Rhyolite, 3.05 Polar Venture, 3.40 Nadmah, 4.10 Tartan Blue.