heulandite

heulandite
/hyooh"leuhn duyt'/, n.
a white or transparent, colorless mineral of the zeolite family, hydrous calcium aluminum silicate, CaAl2Si7O18·6H2O, occurring in basic volcanic rocks in the form of crystals with a pearly luster.
[1815-25; named after Henry Heuland, 19th-century English mineral collector; see -ITE1]

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      hydrated sodium and calcium aluminosilicate mineral in the zeolite family, formulated (Ca,Na)2-3Al3(Al,Si)2Si13O36·12H2O. It forms brittle, transparent, coffin-shaped crystals in various shades of white through red, gray, or brown. Heulandite's molecular structure is an open framework containing six-membered rings of silicate tetrahedra (four oxygen atoms arranged at the points of a triangular pyramid around a central silicon atom) joined in parallel planes. This structure and the substitution of aluminum atoms for some of the silicon atoms give the mineral its cation-exchange properties (dissolved sodium, potassium, calcium, and magnesium readily replacing one another in the molecular structure), making it useful in water softeners. Heulandite is found with other zeolite minerals filling cavities in granites, pegmatites, and basalts. Typical occurrences are in Berufjördhur, Ice.; on islands near Bombay; on the Faroe Islands; and in northeastern New Jersey.

      Heulandite is a member of a group of zeolite minerals with a characteristic platy habit. Others in the group are stilbite, epistilbite, and brewsterite. These minerals have similar modes of occurrences, physical properties, and molecular structures. Stilbite and epistilbite are more common in sheaflike aggregates or crosslike penetration twins than in single crystals. For chemical formulas and detailed physical properties, see zeolite (table).

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Universalium. 2010.

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Look at other dictionaries:

  • Heulandite — Catégorie IX : silicates[1] Heulandite Ca Drio le Pale, Italie (5x4.5 cm) …   Wikipédia en Français

  • Heulandite — is the name of a series of tecto silicate minerals of the zeolite group. Prior to 1997, heulandite was recognized as a mineral species, but a reclassification in 1997 by the International Mineralogical Association changed it to a series name,… …   Wikipedia

  • heulandite — ⇒HEULANDITE, subst. fém. MINÉR. Silicate hydraté naturel d alumine et de chaux, cristallisé dans les cavités des roches volcaniques. La stilbite, qui cristallise en prisme rhomboïdal droit, offre dans ses caractères extérieurs tant d analogie… …   Encyclopédie Universelle

  • Heulandite — Heu land*ite, n. [After Heuland, an English mineralogist.] (Min.) A mineral of the Zeolite family, often occurring in amygdaloid, in foliated masses, and also in monoclinic crystals with pearly luster on the cleavage face. It is a hydrous… …   The Collaborative International Dictionary of English

  • *heulandite — ● heulandite nom féminin (de H. Heuland, nom propre) Aluminosilicate hydraté naturel de calcium, appartenant à la famille des zéolites …   Encyclopédie Universelle

  • heulandite — [hyo͞o′lən dīt΄] n. [named (1822) after Henry Heuland, Eng mineralogist] a semihard, lightweight, monoclinic zeolite, (Na,Ca) 4 6Al6 (Al,Si) 4Si26O72·24H2O …   English World dictionary

  • heulandite — noun A common mineral of the zeolite group with monoclinic crystals, the most usual form being heulandite Ca (Ca,Na)Al(Al,Si)SiO·12HO …   Wiktionary

  • heulandite — noun Etymology: Henry Heuland, 19th century English mineral collector Date: 1822 a zeolite consisting of a hydrous aluminosilicate of sodium and calcium …   New Collegiate Dictionary

  • heulandite — (entrée créée par le supplément) (eu lan di t ) s. f. Terme de minéralogie. Silicate double d alumine et de chaux hydraté, cristallisant en prismes obliques …   Dictionnaire de la Langue Française d'Émile Littré

  • heulandite — heu·land·ite …   English syllables

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