phonolitic /fohn'l it"ik/, adj.
/fohn"l uyt'/, n.
a fine-grained volcanic rock composed chiefly of alkali feldspar and nepheline, some varieties of which split into pieces that ring on being struck.
[1820-30; < F < G Phonolith. See PHONO-, -LITE]

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      any member of a group of extrusive igneous rocks (lavas) that are rich in nepheline and potash feldspar. The typical phonolite is a fine-grained, compact igneous rock that splits into thin, tough plates which make a ringing sound when struck by a hammer, hence the rock's name.

      The most important constituent of phonolite is alkali feldspar, either sanidine or anorthoclase, which forms not only the bulk of the groundmass (matrix) but most of the large crystals (phenocrysts) in porphyritic varieties. Nepheline rarely appears in large crystals but may occur either interstitially or in well-formed microphenocrysts. The principal dark-coloured mineral is pyroxene: (pyroxene) aegirine or titaniferous augite. Pyroxene phenocrysts occur as well-formed crystals; in the groundmass, pyroxene occurs characteristically as slender needles, often abundant enough to colour the rock green. An alkaline amphibole nearly always occurs as phenocrysts; barkevikite, riebeckite, or arfvedsonite are typical. Feldspathoids other than nepheline may be present as accessory minerals; the most common are nosean, sodalite, and leucite.

      Most phonolites are of Tertiary or Recent age and therefore formed within about the last 66 million years. They are common in Europe, as in Auvergne, France; the Eifel plateau and the Laacher See, Germany; the Czech Republic; and the Mediterranean area (chiefly in Italy). They also occur at Cripple Creek, Colorado, and the Black Hills, South Dakota; Devil's Tower, Wyoming, is variously described as tinguaite or phonolite, depending on whether it is considered a volcanic plug or a flow.

      Leucite phonolites are perhaps best known from the vicinity of Naples. Apachite, from the Apache Mountains, Texas, is an amphibole phonolite. Kenyite, from Mount Kenya, in east Africa, is rich in olivine. The phonolite of Olbrück, Ger., a rather popular local building stone, is said to contain about 15 percent nosean and 8 percent leucite. Phonolite trachytes occur on St. Helena and a number of other volcanic islands.

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Universalium. 2010.

Look at other dictionaries:

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  • Phonolite — Pho no*lite, n. [Phono + lite: cf. F. phonolithe.] (Min.) A compact, feldspathic, igneous rock containing nephelite, ha[ u]ynite, etc. Thin slabs give a ringing sound when struck; called also {clinkstone}. [1913 Webster] …   The Collaborative International Dictionary of English

  • phonolite — a kind of volcanic rock which rings when struck, c.1830, from PHONO (Cf. phono ) + LITE (Cf. lite). Replacing Ger. klingstein …   Etymology dictionary

  • phonolite — [fō′nə līt΄] n. [Fr phonolithe < phono (see PHONO ) + lithe (see LITE): transl. of Ger klingstein < klingen, to ring, clink + stein,STONE] a fine grained, extrusive igneous rock consisting chiefly of alkali feldspar and nepheline phonolitic …   English World dictionary

  • Phonolite — Aegirine phonolite. Dark prismatic minerals are aegirine phenocrysts. Phonolite is a rare igneous, volcanic (extrusive) rock of intermediate (between felsic and mafic) composition, with aphanitic to porphyritic texture. The name phonolite comes… …   Wikipedia

  • phonolite — phonolithe ou phonolite [ fɔnɔlit ] n. m. ou f. • 1823; phonolite 1807; de phono et lithe « pierre qui résonne » ♦ Minér. Trachyte feldspathique qui se présente sous forme de laves compactes, sonores sous le choc. Adj. PHONOLITHIQUE ou… …   Encyclopédie Universelle

  • phonolite — noun Etymology: French, from German Phonolith, from phon + lith; from its ringing sound when struck Date: circa 1828 a gray or green volcanic rock consisting essentially of orthoclase and nepheline …   New Collegiate Dictionary

  • phonolite — noun a light coloured rock of volcanic origin composed mostly of alkali feldspars …   Wiktionary

  • phonolite —    A type of volcanic rock, common as lava flows in some areas, that is capable of supporting the formation of extensive lava caves, including those on Mount Suswa in Kenya [9] …   Lexicon of Cave and Karst Terminology

  • phonolite — n. clinkstone, fine grained igneous rock; light colored volcanic rock composed mainly of feldspars (Geology) …   English contemporary dictionary

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