Diaspore
(repeating unit)α-AlO(OH) IMA symbol Dsp[1] Strunz classification 4.FD.10 Crystal system Orthorhombic Crystal class Dipyramidal (mmm)
H–M symbol: (2/m 2/m 2/m) Space group Pbnm Unit cell a = 4.4007(6) Å
b = 9.4253(13) Å
c = 2.8452(3) Å; Z = 4 Identification Color White, pale gray, colorless, greenish gray, brown, pale yellow, pink, purple; may exhibit color change Crystal habit Platy, elongated to acicular crystals; also stalactitic, foliated, scaly, disseminated, and massive 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 6.5–7.0 Luster Adamantine, vitreous, pearly on cleavage faces Diaphaneity Transparent to translucent Specific gravity 3.1–3.4 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: 84–86°
Calculated: 80–84° Dispersion r < v, weak Fusibility Infusible Solubility Insoluble Other characteristics Decrepitates releasing water in closed tube on heating References [2][3]
H–M symbol: (2/m 2/m 2/m)
b = 9.4253(13) Å
c = 2.8452(3) Å; Z = 4
nβ = 1.705–1.725
nγ = 1.730–1.752
Calculated: 80–84°
Diaspore (/ˈdaɪ.əˌspɔːr/) – also called diasporite, empholite, kayserite, or tanatarite – is an aluminium hydroxide oxide mineral, 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.[4] It may be readily distinguished from other colorless transparent minerals with a perfect cleavage and pearly luster (e.g. mica, talc, brucite, and gypsum) by its greater hardness of 6.5–7. Its specific gravity is 3.4. When heated before the blowpipe, it decrepitates violently, breaking up into white pearly scales.[5]
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 Ural Mountains 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.[5]
Diaspore, along with gibbsite and boehmite, is a major component 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, which was coined by René Just Haüy,[6] is from the Ancient Greek διασπείρω meaning "to scatter", in allusion to its decrepitation on heating.[2]
Csarite, ottomanite, Turkizite and zultanite are trade names for gem-quality diaspore (also known as Turkish diaspore) from the İlbir Mountains of southwest Turkey.[7]
References
- ^ Warr, L. N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ a b Handbook of Mineralogy
- ^ a b Klein, Cornelis; Hurlbut, Cornelius S. (1985). Manual of Mineralogy (20th ed.). Wiley. p. 318. ISBN 0-471-80580-7.
- ^ "The mineral diaspore". minerals.net. Retrieved 2014-06-10.
- ^ a b
One or more of the preceding sentences incorporates text from a publication now in the public domain: Spencer, Leonard James (1911). "Diaspore". In Chisholm, Hugh (ed.). Encyclopædia Britannica. Vol. 8 (11th ed.). Cambridge University Press. pp. 168–169. - ^ Spencer 1911.
- ^ Hatipoğlu, Murat; Türk, Necdet; Chamberlain, Steven C.; Akgün, A. Murat (2010). "Gem-quality transparent diaspore (zultanite) in bauxite deposits of the İlbir Mountains, Menderes Massif, SW Turkey". Mineralium Deposita. 45 (2): 201–205. doi:10.1007/s00126-009-0262-2.
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