tachylyte

tachylyte
—tachylitic /tak'euh lit"ik/, adj.
/tak"euh luyt'/, n. Petrog.
a black, glassy form of basalt, readily fusible and of a high luster.
Also, tachylite.
[1865-70; TACHY- + -LYTE2]

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▪ rock
also spelled  tachylite 

      glassy igneous rocks low in silica, such as basalt or diabase. Tachylytes are black with a pitchlike or resinous lustre; in thin sections they are characteristically brown and translucent, and the glass is crowded with granules of magnetite. Tachylytes are found only under conditions that imply rapid cooling, and they are much less common than are the corresponding acid volcanic glasses, principally because of the greater fluidity and greater tendency of basic lavas to crystallize.

      The principal mode of occurrence of tachylyte is as a chilled edge to thin dikes or sills of basalt or diabase; this edge may be only a millimetre or so thick and merges inward into crystalline basalt. Tachylytes of this nature are common among the igneous rocks of Tertiary age in the Inner Hebrides of Scotland. Sometimes tachylyte constitutes almost entire lava flows, as in the Hawaiian Islands; the rapid cooling of the highly fluid lavas of this region has inhibited crystallization, giving rise to vast floods of basaltic glass that contains only minor amounts of crystalline material. Lastly, tachylytes occur as scoria, or bombs, thrown out by basaltic volcanoes; these are well known at Stromboli Island and at Mount Etna in Italy, and in Iceland. Tachylytes readily undergo weathering and alteration and are converted by oxidation and hydration into palagonite, a red, brown, or yellow cryptocrystalline material.

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Universalium. 2010.

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Look at other dictionaries:

  • Tachylyte — Tach y*lyte, n. [Gr. tachy s quick + ? to dissolve.] (Min.) A vitreous form of basalt; so called because decomposable by acids and readily fusible. [1913 Webster] …   The Collaborative International Dictionary of English

  • tachylyte — or tachylite [tak′ə līt΄] n. [Ger tachylit < Gr tachys, swift (see TACHY ) + lytos, soluble < lyein, to dissolve (see LYSIS): from its rapid decomposition in acids] a kind of dark colored, basaltic volcanic glass tachylytic [tak′əlit′ik]… …   English World dictionary

  • Tachylyte — Tachylite Le tachylyte est principalement composé de basaltes et de roches volcaniques vitreuses. Le tachylyte est produit suite au refroidissement rapide de la lave basaltique, par exemple, au fond de l océan à la suite de l activité volcanique …   Wikipédia en Français

  • tachylyte — noun A black, vitreous basalt of volcanic origin …   Wiktionary

  • tachylyte — tachy·lyte …   English syllables

  • tachylyte — /ˈtækəlaɪt/ (say takuhluyt) noun a black, glassy form of basalt, readily fusible and of a high lustre. Also, tachylite. {German Tachylit, from Greek tachy tachy + lytos soluble} –tachylytic /tækəˈlɪtɪk/ (say takuh litik), adjective …  

  • tachylyte — …   Useful english dictionary

  • tach|y|lyt|ic — «TAK uh LIHT ihk», adjective. 1. composed of tachylyte. 2. resembling tachylyte. 3. containing tachylyte …   Useful english dictionary

  • Volcanic glass — A sand grain of volcanic glass under the petrographic microscope. Its amorphous nature makes it go extinct in cross polarized light (bottom frame). Scale box in millimeters. Volcanic glass is the amorphous (uncrystallized) product of rapidly… …   Wikipedia

  • Mafic — is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term is a portmanteau of the words magnesium and ferric .[1] Most mafic minerals are dark in color and the relative density is greater than 3. Common… …   Wikipedia

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