Sanidine


Sanidine

Sanidine is the high temperature form of potassium feldspar (K,Na)(Si,Al)4O8. [Mineral Handbook http://www.minsocam.org/msa/Handbook/Sanidine.PDF ] Sanidine most typically occurs in felsic volcanic rocks such as obsidian, rhyolite and trachyte. Sanidine crystallizes in the monoclinic crystal system. Orthoclase is a monoclinic polymorph stable at lower temperatures. At yet lower temperatures, microcline, a triclinic polymorph of potassium feldspar, is stable.

Due to the high temperature and rapid quenching, sanidine can contain more sodium in its structure than the two polymorphs that equilibrated at lower temperatures. Sanidine and high albite constitute a solid solution series with intermediate compositions termed anorthoclase. Exsolution of an albite phase does occur; resulting cryptoperthite can best be observed in electron microprobe images.

References

* Hurlbut, Cornelius S.; Klein, Cornelis, 1985, "Manual of Mineralogy", 20th ed., Wiley, ISBN 0-471-80580-7
* [http://www.webmineral.com/data/Sanidine.shtml Webmineral data]
* [http://www.mindat.org/min-3521.html Mindat]


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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 — ● 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 — 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,… …   Universalium

  • 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} …   Australian English dictionary

  • sanidine — …   Useful english dictionary


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