Diaspore
| Diaspore | |
|---|---|
 | |
| General | |
| Category | Oxide mineral |
| Formula (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 toacicularcrystals; 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 scalehardness | 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] |
Diaspore(/ˈdaɪ.əˌspɔːr/) – also calleddiasporite,empholite,kayserite,ortanatarite– is analuminium hydroxide oxidemineral, α-AlO(OH), crystallizing in theorthorhombicsystem andisomorphouswithgoethite.It occurs sometimes as flattened crystals, but usually as lamellar or scaly masses, the flattened surface being a direction of perfectcleavageon which thelustreis markedly pearly in character. It is colorless or greyish-white, yellowish, sometimes violet in color, and varies fromtranslucent 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,andgypsum) by its greater hardness of 6.5–7. Itsspecific gravityis 3.4. When heated before the blowpipe, itdecrepitatesviolently, breaking up into white pearly scales.[5]
The mineral occurs as an alteration product ofcorundumoremeryand is found in granularlimestoneand other crystalline rocks. Well-developed crystals are found in the emery deposits of theUral Mountainsand atChester, Massachusetts,and inkaolinat Schemnitz inHungary.If obtainable in large quantity, it would be of economic importance as a source ofaluminium.[5]
Diaspore, along withgibbsiteandboehmite,is a major component of the aluminiumorebauxite.[3]
It was first described in 1801 for an occurrence in Mramorsk Zavod,Sverdlovskaya Oblast,MiddleUrals,Russia.The name, which was coined byRené Just Haüy,[6]is from theAncient Greekδιασπείρωmeaning "to scatter", in allusion to its decrepitation on heating.[2]
Csarite,ottomanite,Turkiziteandzultaniteare trade names for gem-quality diaspore (also known as Turkish diaspore) from theİlbir Mountainsof southwestTurkey.[7]
References[edit]
- ^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.S2CID235729616.
- ^abHandbook of Mineralogy
- ^abKlein, Cornelis; Hurlbut, Cornelius S. (1985).Manual of Mineralogy(20th ed.).Wiley.p. 318.ISBN0-471-80580-7.
- ^"The mineral diaspore".minerals.net.Retrieved2014-06-10.
- ^abOne or more of the preceding sentences incorporates text from a publication now in thepublic domain:Spencer, Leonard James(1911). "Diaspore".InChisholm, 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.
