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Diaspore

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Formula:
AlO(OH)
System:
Orthorhombic
Colour:
white, brown, ...
Hardness:
6½ - 7
Member of:
Name:
Named in 1801 by Abbé Rene Just Haüy from the Greek διασπείρειυ, to scatter, in allusion to the usual decrepitaton in the blowpipe flame.
Dimorph of:
Beware! Certain dealers (especially on ebay) have been offering samples of a whitish-metallic feathery material as "diaspore". It appears to be metallic aluminium plumes formed from metal dripping from smelters, and is not either diaspore or a mineral.

Visit gemdat.org for gemological information about Diaspore.

Classification of Diaspore

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
4.FD.10

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
F : Hydroxides (without V or U)
D : Hydroxides with OH, without H2O; chains of edge-sharing octahedra
6.1.1.1

6 : HYDROXIDES AND OXIDES CONTAINING HYDROXYL
1 : XO(OH)
7.6.2

7 : Oxides and Hydroxides
6 : Oxides of Al
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First Recorded Occurrence of Diaspore

Year of Discovery:
1801

Occurrences of Diaspore

Geological Setting:
With other minerals in bauxite deposits.

Physical Properties of Diaspore

Vitreous, Pearly
Diaphaneity (Transparency):
Transparent, Translucent
Comment:
Pearly on cleavage
Colour:
white, brown, colourless, pale yellow, greyish, greenish grey, lilac, pinkish
Streak:
white
Hardness (Mohs):
6½ - 7
Tenacity:
Very brittle
Cleavage:
Perfect
{010} perfect; {110} distinct; {100} in traces
Fracture:
Conchoidal
Density:
3.2 - 3.5 g/cm3 (Measured)    3.38 g/cm3 (Calculated)

Crystallography of Diaspore

Crystal System:
Orthorhombic
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Cell Parameters:
a = 4.4007(6) Å, b = 9.4253(13) Å, c = 2.8452(3) Å
Ratio:
a:b:c = 0.467 : 1 : 0.302
Unit Cell Volume:
V 118.01 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Crystals commonly thin platy {010} and elongated [001]; acicular at times [001]; tabular {100}, rare. Faces in zone [010] striated [010]; in zone [001] striated [001]; and in zone [012] striated [012]. Foliated massive; thin scales. Stalactitic at times.
Twinning:
n {61, or on {021}, uncommon, with a reentrant angle of about 60°±, producing psedohexagonal aggregates, normal to the pseudhexagonal axis a[100].
Comment:
Setting is Pbnm

Crystallographic forms of Diaspore

Crystal Atlas:
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Diaspore no.5 - Goldschmidt (1913-1926)
Diaspore no.8 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by www.smorf.nl.

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Edge Lines | Miller Indicies | Axes

Transparency
Opaque | Translucent | Transparent

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Along a-axis | Along b-axis | Along c-axis | Start rotation | Stop rotation

Optical Data of Diaspore

Type:
Biaxial (+)
RI values:
nα = 1.682 - 1.706 nβ = 1.705 - 1.725 nγ = 1.730 - 1.752
2V:
Measured: 84° to 86°, Calculated: 80° to 84°
Max Birefringence:
δ = 0.048
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
High
Dispersion:
weak r
Pleochroism:
Strong
Comments:
In thick plates
1st. direction: violet-blue
2nd. direction: plum-red
3rd. direction: pale asparagus-green

Chemical Properties of Diaspore

Formula:
AlO(OH)
Essential elements:
All elements listed in formula:
Common Impurities:
Fe,Mn,Cr,Si

Relationship of Diaspore to other Species

Member of:
Other Members of Group:
BracewelliteCrO(OH)
GroutiteMn3+O(OH)
Montroseite(V3+,Fe3+)O(OH)
TsumgalliteGaO(OH)
4.FD.05SpertiniiteCu(OH)2
4.FD.10BracewelliteCrO(OH)
4.FD.10GroutiteMn3+O(OH)
4.FD.10GuyanaiteCrO(OH)
4.FD.10Montroseite(V3+,Fe3+)O(OH)
4.FD.10TsumgalliteGaO(OH)
4.FD.15ManganiteMn3+O(OH)
4.FD.20Yttrotungstite-(Y)YW2O6(OH)3
4.FD.20Yttrotungstite-(Ce)(Ce,Nd,Y)W2O6(OH)3
4.FD.20Unnamed (Nd-analogue of Yttrotungstite-(Ce))(Nd,Ce,La)W2O6(OH)3
4.FD.25FrankhawthorneiteCu2Te6+O4(OH)2
4.FD.30KhinitePb2+Cu32+[Te6+O6](OH)2
4.FD.30Khinite-3TPb2+Cu32+Te6+O6(OH)2
7.6.1CorundumAl2O3
7.6.2BöhmiteAlO(OH)
7.6.4GibbsiteAl(OH)3
7.6.5BayeriteAl(OH)3
7.6.6NordstranditeAl(OH)3
7.6.7DoyleiteAl(OH)3
7.6.8Akdalaite4Al2O3 · H2O

Other Names for Diaspore

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Diaspore

Reference List:
Ewing (1935), Journal Chem. Phys.: 3: 203.

Palache, Charles, Harry Berman & Clifford Frondel (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged: 675-679.

Physics and Chemistry of Minerals: 5: 179-200.

Isetti G., Penco A.M. (1968) - Studio sul pleocroismo infrarosso del diasporo. Periodico di mineralogia – Roma, pp. 31-43.

Pawley, A.R., Redfern, S.A.T., and Holland, T.J.B. (1996), Volume behavior of hydrous minerals at high pressures and temperatures: 1. Thermal expansion of lawsonite, zoisite, clinozoisite, and diaspore. American Mineralogist: 81: 335-340.

Internet Links for Diaspore

Specimens:
The following Diaspore specimens are currently listed for sale on minfind.com.

Localities for Diaspore

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
Mineral and/or Locality  
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