sanidinic /san'i din"ik/, adj.
/san"i deen', -din/, n. Mineral.
a glassy, often transparent variety of orthoclase in which sodium may replace as much as 50 percent of the potassium: forms phenocrysts in some igneous rocks.
[1805-15; < G Sanidin, equiv. to Gk sanid- (s. of sanís plank) + G -in -INE2]

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      alkali feldspar mineral, a high-temperature form of potassium aluminosilicate (KAlSi3O8) that sometimes occurs in surface rocks. Sanidine forms colourless or white, glassy, transparent crystals in acidic volcanic rocks.

      Because sanidine that occurs in the Earth's crust has cooled quickly (its structure is stable only above 700° C [1,300° F]), it has trapped a disordered distribution of the aluminum and silicon atoms in its aluminosilicate crystal framework. Among the various forms of potassium aluminosilicate, there is a complete variation in ordering from the fully random arrangement in high-sanidine (a very-high-temperature form), through sanidine and then orthoclase, to the fully ordered arrangement in microcline.

      The name anorthoclase is applied to the intermediate members of the high-albite–sanidine series that contain less than 40 percent KAlSi3O8. Anorthoclase occurs, often as crystals, only in sodium-rich volcanic rocks, such as the andesitic lavas of Pantelleria, southwest of Sicily. Other occurrences include Kilimanjaro, Tanzania; Mt. Kenya, Kenya; Yellowstone National Park, Wyoming; and the German Rhineland.

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Universalium. 2010.

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Look at other dictionaries:

  • Sanidine — Catégorie IX : silicates[1] Azulicite (Var. Sanidine) Mina La Pili, Chihuahua, Mexique. (3.5x2.2 cm) …   Wikipédia en Français

  • Sanidine — is the high temperature form of potassium feldspar (K,Na)(Si,Al)4O8. [Mineral Handbook ] Sanidine most typically occurs in felsic volcanic rocks such as obsidian, rhyolite and trachyte. Sanidine… …   Wikipedia

  • sanidine — ● sanidine nom féminin (grec sanidion, planchette) Variété de feldspath potassique que l on trouve dans les roches volcaniques. ⇒SANIDINE, subst. fém. MINÉR. Variété de feldspath orthose que l on trouve dans les roches volcaniques. Le trachyte… …   Encyclopédie Universelle

  • Sanidine — San i*dine, n. [Gr. ?. ?, a board. So called in allusion to the tabular crystals.] (Min.) A variety of orthoclase feldspar common in certain eruptive rocks, as trachyte; called also {glassy feldspar}. [1913 Webster] …   The Collaborative International Dictionary of English

  • sanidine — noun A variety of orthoclase feldspar found as tabular crystals embedded in volcanic rocks. It sometimes reflects a blue sheen along crystal planes. This phenomenon is called adularescence, and sanidine with this property is called moonstone.… …   Wiktionary

  • sanidine — sanidinas statusas T sritis chemija apibrėžtis Mineralas. formulė K[AlSi₃O₈] atitikmenys: angl. sanidine rus. санидин …   Chemijos terminų aiškinamasis žodynas

  • sanidine — [ sanɪdi:n] noun a glassy mineral of the alkali feldspar group. Origin C19: from Gk sanis, sanid board + ine4 …   English new terms dictionary

  • sanidine — san·i·dine …   English syllables

  • sanidine — /ˈsænədin/ (say sanuhdeen) noun a mineral form of potash felspar, similar to orthoclase and occurring in some lavas. {German} …  

  • sanidine — …   Useful english dictionary

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