Grey, red, black, altered white/tan, flow-banded pumice dacite

Dacite (IPA: /ˈdeɪsʌɪt/) is an igneous, volcanic rock with a high iron content. It is intermediate in compositions between andesite and rhyolite, and, like andesite, it consists mostly of plagioclase feldspar with biotite, hornblende, and pyroxene (augite and/or enstatite). It has an aphanitic to porphyritic texture with quartz as rounded, corroded phenocrysts, or as an element of the ground-mass. The relative proportions of feldspars and quartz in dacite, and in many other volcanic rocks, are illustrated in the QAPF diagram. Dacite is also defined by silica and alkali contents in the TAS classification. Download high resolution version (1200x423, 113 KB)Photograph by Daniel Mayer. ... Download high resolution version (1200x423, 113 KB)Photograph by Daniel Mayer. ... Articles with similar titles include the NATO phonetic alphabet, which has also informally been called the “International Phonetic Alphabet”. For information on how to read IPA transcriptions of English words, see IPA chart for English. ... Volcanic rock on North America Plutonic rock on North America Igneous rocks (etymology from latin ignis, fire) are rocks formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... This article is about volcanoes in geology. ... “Rock” redirects here. ... A sample of andesite (dark groundmass) with amygdaloidal vesicules filled with zeolite. ... Rhyolite This page is about a volcanic rock. ... Lunar Ferroan Anorthosite #60025 (Plagioclase Feldspar). ... This article does not cite any references or sources. ... A Biotite slice Biotite is a common phyllosilicate mineral that contains potassium, magnesium, iron and aluminium. ... Amphibole (Hornblende) Hornblende is a complex inosilicate series of minerals. ... Figure 1:Mantle-peridotite xenolith with green peridot olivine and black pyroxene crystals from San Carlos Indian Reservation, Gila Co. ... Augite is a single chain inosilicate mineral described chemically as (Ca,Mg,Fe)SiO3 or calcium magnesium iron silicate. ... The pyroxene silicate minerals enstatite (MgSiO3) and ferrosilite (FeSiO3) form a complete solid solution series and are common rock-forming minerals found in igneous and metamorphic rocks and meteorites. ... An aphanite is an igneous rock with a fine-grained structure. ... (For other meanings of Porphyr, see Porphyry) The baptismal font in the Cathedral of Magdeburg is made of rose porphyry from a site near Assuan, Egypt Porphyry is a very hard red, green or purple igneous rock consisting of large-grained crystals, such as feldspar or quartz, dispersed in a... For other uses, see Quartz (disambiguation). ... Example of phenocrysts in rhomb porphyry from the Oslo rift area in Norway A phenocryst is a relatively large and usually conspicuous crystal formed in the mass of a porphyritic igneous rock. ... A QAPF diagram is a double triangle diagram which is used to classify igneous rocks based on mineralogic composition. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... The TAS classification can be used to assign names to many common types of volcanic rocks based upon the relationships between the combined alkali content and the silica content. ...

The plagioclase ranges from oligoclase to andesine and labradorite, and is often very zoned. Sanidine occurs also in some dacites, and when abundant gives rise to rocks that form transitions to the rhyolites. The biotite is brown; the hornblende brown or greenish brown; and the augite is usually green. Oligoclase is a rock-forming mineral belonging to the plagioclase feldspars. ... Andesine is a feldspar mineral, a part of the plagioclase series. ... Labradorite, a feldspar mineral, is a member of the plagioclase series. ... Sanidine is the high temperature form of potassium feldspar ((K,Na)(Si,Al)4O8) which occurs in felsic volcanic rocks such as rhyolite and trachyte. ...

The groundmass of these rocks is often microcrystalline, with a web of minute feldspars mixed with interstitial grains of quartz or tridymite; but in many dacites it is largely vitreous, while in others it is felsitic or cryptocrystalline. In hand specimen many of the hornblende and biotite dacites are grey or pale brown and yellow rocks with white feldspars, and black crystals of biotite and hornblende. Other dacites, especially augite and enstatite dacites, are darker colored. Tridymite Tridymite is a high-temperature polymorph of quartz and usually occurs as minute tabular white or colorless pseudo-hexagonal triclinic crystals, or scales, in cavities in acidic volcanic rocks. ...

The rocks of this group occur in Romania, Almeria (Spain), Argyll and other parts of Scotland, Bardon Hill in Leicestershire, New Zealand, the Andes, Martinique, Nevada and other regions of western North America, Greece as well as other places. They are mostly associated with andesites and trachytes, and form lava flows, dikes, and in some cases form massive intrusions in the centers of volcanoes. Dacite is an important rock type at Mount St. Helens. Almer a (2003 pop. ... Argyll, archaically Argyle (Airthir-Ghaidheal in Gaelic, translated as [the] East Gael, or [the] East Irish), sometimes called Argyllshire, is a traditional county of Scotland. ... This article is about the country. ... Bardon Hill, near Coalville, is the highest point in the English county of Leicestershire, 278 metres (912 feet) above sea level. ... Leicestershire ( IPA: (RP), IPA: (locally)), abbreviation Leics. ... This article is about the mountain system in South America. ... This article is about the U.S. State of Nevada. ... North America North America is a continent[1] in the Earths northern hemisphere and (chiefly) western hemisphere. ... A sample of trachyte Trachyte is an igneous, volcanic rock with an aphanitic to porphyritic texture. ... In computer programming jargon, lava flow is a problem in which computer code, usually written under less than optimal conditions, is put into production and then built on when still in a developmental state. ... A dike in geology refers to a tabular intrusive igneous body. ... For other uses, see Volcano (disambiguation). ... For the mountain in California, see Mount Saint Helena. ...

The word dacite comes from Dacia, a province of the Roman Empire which lay between the Danube River and Carpathian Mountains (now modern Romania) where the rock was first described. Dacia, in ancient geography the land of the Daci, named by the ancient Greeks Getae, was a large district of Southeastern Europe, bounded on the north by the Carpathians, on the south by the Danube, on the west by the Tisa, on the east by the Tyras or Nistru, now... For other uses, see Roman Empire (disambiguation). ... Length 2,888 km Elevation of the source 1,078 m Average discharge 30 km before Passau: 580 m³/s Vienna: 1,900 m³/s Budapest: 2,350 m³/s just before Delta: 6,500 m³/s Area watershed 817,000 km² Origin Black Forest (Schwarzwald-Baar, Baden- Württemberg... Satellite image of the Carpathians. ...

This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain. Encyclopædia Britannica, the eleventh edition The Encyclopædia Britannica Eleventh Edition (1910–1911) is perhaps the most famous edition of the Encyclopædia Britannica. ... The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ...