Rhyolite is an igneous, volcanic rock, of felsic ( silica-rich) composition (typically > 69% SiO 2 – see the TAS classification). It may have any texture from glassy to aphanitic to porphyritic. The mineral assemblage is usually quartz, sanidine and plagioclase (in a ratio > 2:1 – see the QAPF diagram). Biotite and hornblende are common accessory minerals. It is the extrusive equivalent to granite.
Rhyolite can be considered as the extrusive equivalent to the
plutonic granite rock, and consequently, outcrops of rhyolite may bear a resemblance to granite. Due to their high content of silica and low iron and magnesium contents, rhyolitic magmas form highly viscous lavas. They also occur as breccias or in volcanic plugs and dikes. Rhyolites that cool too quickly to grow crystals form a natural glass or vitrophyre, also called obsidian. Slower cooling forms microscopic crystals in the lava and results in textures such as flow foliations, spherulitic, nodular, and lithophysal structures. Some rhyolite is highly vesicular pumice. Many eruptions of rhyolite are highly explosive and the deposits may consist of fallout tephra/ tuff or of ignimbrites.
Eruptions of rhyolite are relatively rare compared to eruptions of less felsic lavas. Only three eruptions of rhyolite have been recorded since the start of the 20th century: at the
St. Andrew Strait volcano in Papua New Guinea, Novarupta volcano in Alaska, and Chaiten in southern Chile.
Rhyolite has been found on islands far from land, but such oceanic occurrences are rare.
Rhyolite in the Kaldaklofsfjöll, Landmannalaugar, Iceland
Cascade Range 
Cobalt, Ontario  Sheep Creek, Idaho
Rhyolite, Nevada was named after a rhyolite deposit that characterised the area. 
Wichita Mountains within the Southern Oklahoma Aulacogen
St. Francois Mountains
Mount Jasper, Berlin, New Hampshire
Crater Lake, Oregon 
Palisade Head, a formation found at Tettegouche State Park, Minnesota Mount Kineo, a volcanic plug; an iconic mountain feature located in Moosehead Lake, Rockwood, Maine, United States
The name rhyolite was introduced into
geology in 1860 by the German traveler and geologist Ferdinand von Richthofen   from the Greek word  rhýax ("a stream of lava") and the rock name suffix "-lite". 
Quarrying by Native Americans
North American pre-historic times, rhyolite was quarried extensively in eastern Pennsylvania in the United States. Among the leading quarries was the Carbaugh Run Rhyolite Quarry Site in Adams County. Rhyolite was mined there starting 11,500 years ago. Tons of rhyolite were traded across the  Delmarva Peninsula, because the rhyolite kept a sharp point when  knapped and was used to make spear points and arrowheads.
Comendite – A hard, peralkaline igneous rock, a type of light blue grey rhyolite
List of rock types – A list of rock types recognized by geologists
Pantellerite – A peralkaline rhyolite type of volcanic rock Thunderegg – A nodule-like rock, that is formed within rhyolitic volcanic ash layers
^ a b c d The Illustrated Encyclopedia of Rocks of the World by John Farndon, page 54.
^ J. Martí, G.J. Aguirre-Díaz, A. Geyer. "The Gréixer rhyolitic complex (Catalan Pyrenees): an example of Permian caldera".
Workshop on Collapse Calderas – La Réunion 2010. . IAVCEI – Commission on Collapse Calderas
Cascades Volcano Observatory. "Cascades Volcano Observatory". usgs.gov . Retrieved . 19 January 2015
ROBERT CINITS. "The Proteus Property" (PDF).
"Rhyolite Ghost Town" . Retrieved . 2009-12-22
"Yandang Shan". Archived from the original on 2016-02-17 . Retrieved . 2011-12-22
Richthofen, Ferdinand Freiherrn von (1860). "Studien aus den ungarisch-siebenbürgischen Trachytgebirgen" [Studies of the trachyte mountains of Hungarian Transylvania]. Jahrbuch der Kaiserlich-Königlichen Geologischen Reichsanstalt (Wein) [Annals of the Imperial-Royal Geological Institute of Vienna] (in German). 11: 153–273.
Simpson, John A.; Weiner, Edmund S. C., eds. (1989). Oxford English Dictionary. 13 (2nd ed.). Oxford: Oxford University Press. p. 873.
Young, Davis A. (2003). Mind Over Magma: The Story of Igneous Petrology. Princeton University Press. p. 117. ISBN . 0-691-10279-1
"Definition of RHYOLITE". www.merriam-webster.com.
"Definition of LITE". www.merriam-webster.com.
^ a b
Fergus, Charles (2001). Natural Pennsylvania: Exploring the State Forest Natural Areas. Stackpole Books. p. 30. OCLC 47018498.
Bricker, Dakota. "Snaggy Ridge Indian Rhyolite Quarries". Mercersburg Historical Society . Retrieved . 2019-01-20
Wikimedia Commons has media related to . Rhyolite