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Trachyte |
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trachyteLight-coloured, very fine-grained igneous rock composed chiefly of alkali feldspar with only minor mafic minerals (biotite, hornblende, or pyroxene). Trachyte is commonly found in volcanic regions; like many volcanic rocks, it shows a streaked or banded structure due to flowing of the congealing lava. trachyte [′tra‚kīt] (petrology) The light-colored, aphanitic rock (the volcanic equivalent of syenite), composed largely of alkali feldspar with minor amounts of mafic minerals. Trachyte a cenotypal extrusive, usually porphyritic rock. Porphyritic phenocrysts and microlites embedded in volcanic glass are represented by sanidine; neutral and acid plagioclase, biotite, pyroxene, or amphibole are encountered in lesser amounts. Trachyte is the extrusive equivalent of syenite. It consists of up to 60 percent silica and up to 10 percent alkalies. The rock is rough to the touch. There are glassy trachytes, such as obsidians and pumices, and trachytic tuffs. Trachytes grade into liparites, andesites, and basalts. They are found in the Caucasus and, outside the USSR, in Italy and France. Trachyte is a relatively rare rock. (See also.) Want to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit the webmaster's page for free fun content. |
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No references found | The mineral occurrences are hosted by a highly mixed sequence of andesitic to locally trachytic volcanics, volcaniclastic sediments, and minor limestone. |
trachytic |
Trachurus Trachurus Trachurus symmetricus Trachurus trachurus Trachyandesite Trachyandra trachybasalt Trachycarpous Trachycarpus Trachylida Trachylina Trachylina Trachymedusae Trachymedusae Trachymene Trachyonychia trachyphonia trachyphonia trachyphonia Trachypremnon Trachypsammiacea Trachypteridae Trachyspermous Trachyspermum ammi Trachystomata Trachystomata trachyte trachyte trachytes trachytes trachytic Trachytic TextureTrachytoid trachytoid texture Traci Traci Traci tracing tracing tracing tracing tracing tracing back Tracing Change Notice Tracing cloth Tracing cloth tracing distortion Tracing Management Technology tracing paper tracing paper tracing routine tracing routine tracings tracings tracings tracings, pantographic TRACIR track track track track | |||||||
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