Diaspore

Diaspore
Diaspore

Diaspore from Slovakia
General
Category Oxide mineral
Chemical formula α-AlO(OH)
Strunz classification 04.FD.10
Crystal symmetry Orthorhombic 2/m 2/m 2/m
Unit cell a = 4.4007(6) Å, b = 9.4253(13) Å, c = 2.8452(3) Å; Z = 4
Identification
Crystal habit Platey, elongated to acicular crystals; also stalactitic, foliated, scaly, disseminated and massive
Crystal system Orthorhombic dipyramidal
Twinning Forms heart shaped twins on {021} or pseudohexagonal aggregates
Cleavage {010} perfect, {110} distinct, {100} in traces
Fracture Conchoidal
Tenacity Very brittle
Mohs scale hardness 6.5 - 7
Luster Adamantine, vitreous, pearly on cleavage faces
Diaphaneity Transparent to translucent
Specific gravity 3.2 - 3.5
Optical properties Biaxial (+)
Refractive index nα = 1.682 - 1.706 nβ = 1.705 - 1.725 nγ = 1.730 - 1.752
Birefringence δ = 0.048
Pleochroism Strong
2V angle Measured: 84° to 86°, Calculated: 80° to 84°
Dispersion r < v, weak
Fusibility Infusible
Solubility Insoluble
Other characteristics Decrepitates releasing water in closed tube on heating
References [1][2][3]

Diaspore is a native aluminium oxide hydroxide, α-AlO(OH), crystallizing in the orthorhombic system and isomorphous with goethite. It occurs sometimes as flattened crystals, but usually as lamellar or scaly masses, the flattened surface being a direction of perfect cleavage on which the lustre is markedly pearly in character. It is colorless or greyish-white, yellowish, sometimes violet in color, and varies from translucent to transparent. It may be readily distinguished from other colorless transparent minerals with a perfect cleavage and pearly luster, like mica, talc, brucite, and gypsum by its greater hardness of 6.5 - 7. The specific gravity is 3.4. When heated before the blowpipe it decrepitates violently, breaking up into white pearly scales.

Twinned crystal of diaspore from Mugla Province, Aegean Region, Turkey (1.8 x .6 x .4 cm)

The mineral occurs as an alteration product of corundum or emery and is found in granular limestone and other crystalline rocks. Well-developed crystals are found in the emery deposits of the Urals and at Chester, Massachusetts, and in kaolin at Schemnitz in Hungary. If obtainable in large quantity, it would be of economic importance as a source of aluminium.

Diaspore along with gibbsite and boehmite are the major components of the aluminium ore bauxite.[3]

It was first described in 1801 for an occurrence in Mramorsk Zavod, Sverdlovskaya Oblast, Middle Urals, Russia. The name is from the Greek for διασπείρειυ, to scatter, in allusion to its decrepitation on heating.[1][2]

Other names for diaspore include empholite, kayserite, tanatarite and spelling variations of these.

Zultanite is a gem quality form of diaspore from Turkey.[4]

See also

References

  1. ^ a b Handbook of Mineralogy
  2. ^ a b Mindat.org
  3. ^ a b Klein, Cornelis and Cornelius S. Hurlbut, Manual of Mineralogy, Wiley, 1985, 20th ed. p.318 ISBN 0-471-80580-7
  4. ^ Mindat - Zultanite

 Chisholm, Hugh, ed (1911). "Diaspore". Encyclopædia Britannica (11th ed.). Cambridge University Press.  This article incorporates text from a publication now in the public domainChisholm, Hugh, ed (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press. 


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  • Diaspore — Di a*spore, n. [From Gr. ? a scattering; dia through, asunder + ? to sow, scatter like seed: cf. F. diaspore.] (Min.) A hydrate of alumina, often occurring in white lamellar masses with brilliant pearly luster; so named on account of its… …   The Collaborative International Dictionary of English

  • Diaspore — ist der botanische Sammelbegriff für alle verbreitungsfördernden Einheiten wie Samen, Teilfrüchte, Früchte, Fruchtstände, Sporen, Bulbillen oder sonstige vegetative Brutknospen, die der Ausbreitung von Pflanzen oder Pilzen dienen. Der im… …   Deutsch Wikipedia

  • diaspore — diaspore. См. диаспора. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Diaspore — Diaspore, funktionelle Ausbreitungseinheit von Pflanzen, d.h. Teile wie Spore, Samen, Teilfrucht, Frucht oder auch ganzer Fruchtstand, aus denen neue Pflanzen hervorgehen können …   Deutsch wörterbuch der biologie

  • diaspore — [dī′ə spôr΄] n. [< Gr diaspora: see DIASPORA] a native hydrate of aluminum, Al2O3·H2O, which crackles and disperses when heated …   English World dictionary

  • Diaspore — Cette page d’homonymie répertorie les différents sujets et articles partageant un même nom. En botanique le terme diaspore désigne tout élément permettant d accomplir la dissémination d une espèce végétale (par reproduction ou par multiplication… …   Wikipédia en Français

  • Diaspore — diaspora statusas T sritis ekologija ir aplinkotyra apibrėžtis Galinti plisti augalo dalis (spora, sėkla, svogūnėlis, gniužulo dalis), iš kurios gali išaugti naujas augalas. atitikmenys: angl. diaspore vok. Diaspore, f; Verbreitungseinheit, f rus …   Ekologijos terminų aiškinamasis žodynas

  • diaspore — diaspora statusas T sritis ekologija ir aplinkotyra apibrėžtis Galinti plisti augalo dalis (spora, sėkla, svogūnėlis, gniužulo dalis), iš kurios gali išaugti naujas augalas. atitikmenys: angl. diaspore vok. Diaspore, f; Verbreitungseinheit, f rus …   Ekologijos terminų aiškinamasis žodynas

  • diaspore — /duy euh spawr , spohr /, n. 1. a mineral, aluminum oxyhydroxide, AlO(OH), occurring in crystals, or more usually in lamellar or scaly masses: a principal constituent of bauxite and an important source of aluminum. 2. Bot. a disseminule, esp. one …   Universalium

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