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Böhmite

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Saga 1 Quarry, Sagåsen (Strandåsen), Mørje, Porsgrunn, Telemark, Norway
© OT. Ljostad

Show Böhmite Photos (12)
Formula:
AlO(OH)
System:OrthorhombicColour:White, pale greyish ...
Hardness:3½
Name:For Johannes Böhm (1857-1938), German geologist, who first studied the species.


A major constituent of the aluminium ore Bauxite.

Dimorphous with Diaspore and isostructural with Lepidocrocite.

Classification of Böhmite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:4/F.06-20
Nickel-Strunz 10th (pending) edition ID:4.FE.15

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
F : Hydroxides (without V or U)
E : Hydroxides with OH, without H2O; sheets of edge-sharing octahedra
Dana 8th edition ID:6.1.2.1

6 : HYDROXIDES AND OXIDES CONTAINING HYDROXYL
1 : XO(OH)
Hey's CIM Ref.:7.6.2

7 : Oxides and Hydroxides
6 : Oxides of Al
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Type Occurrence of Böhmite

Type Locality:Mas Rouge, Les Baux-de-Provence, Bouches-du-Rhône, Provence-Alpes-Côte d'Azur, France
Geological Setting of type material:Bauxite deposit
Associated Minerals at type locality:
KaoliniteGibbsiteDiaspore

Occurrences of Böhmite

Geological Setting:In bauxite, laterite or fireclay deposits; as a low-temperature hydrothermal decomposition product in nepheline pegmatites, syenites and ocean-ridge basalts.

Physical Properties of Böhmite

Lustre:Vitreous, Pearly
Diaphaneity (Transparency):Translucent
Colour:White, pale greyish brown; yellowish or reddish when impure; colourless in thin section
Streak:White
Hardness (Mohs):3½
Cleavage:Very Good
on {010}, good on {100}, and poor on {001}
Density (measured):3.02 - 3.05 g/cm3
Density (calculated):3.08 g/cm3

Crystallography of Böhmite

Crystal System:Orthorhombic
Class (H-M):mmm (2/m 2/m 2/m) - Dipyramidal
Cell Parameters:a = 3.693Å, b = 12.221Å, c = 2.865Å
Ratio:a:b:c = 0.302 : 1 : 0.234
Unit Cell Volume:V 129.30 ų (Calculated from Unit Cell)
Z:4
Morphology:Rarely tabular to stout prismatic crystals, to 2 mm, showing {001}, {110}, {101}, {111}, {221}; commonly extremely fine-grained, in pisolitic aggregates or disseminated.
X-Ray Powder Diffraction:
d-spacingIntensity
6.11 (100)
3.15 (60)
2.347 (60)
1.862 (20)
1.850 (20)
1.308 (15)
Comments:Recorded on material from Hurunui Peak, New Zealand

Optical Data of Böhmite

Type:Biaxial (+)
RI values: nα = 1.644 - 1.648 nβ = 1.654 - 1.657 nγ = 1.661 - 1.668
2V:Measured: 74° to 88°, Calculated: 80°
Maximum Birefringence:δ = 0.017 - 0.020

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Moderate
Dispersion:weak

Chemical Properties of Böhmite

Formula:
AlO(OH)
Essential elements:Al, H, O
All elements listed in formula:Al, H, O
Analytical Data:(1) Chemical analysis of material from Vishnevy Mts, Urals, Russia
(2) Electron microprobe analysis of material from Hurunui Peak, New Zealand; water content calculated from stoichiometry
         (1)      (2)

SiO2    (2.11)   (0.76)
TiO2             (0.03)
Al2O3  (81.60)  (83.84)
Ga2O3   (0.05)
Fe2O3   (0.58)   (0.53)
MgO              (0.02)
CaO     (0.26)   (0.08)
H2O    (15.31)  (15.05)

sum     99.91   100.31 wt.-%
Empirical Formula:
Al
 
0.98
[O
 
0.96
(OH)
 
1.04
]
 
=2.00
 (1); Al
 
0.98
Si
 
0.01
O(OH) (2)

Relationship of Böhmite to other Species

Related Minerals - Nickel-Strunz Grouping):

- +
4.FE.05Amakinite
(Fe
2+
 
,Mg)(OH)
 
2
4.FE.05Brucite
Mg(OH)
 
2
4.FE.05Portlandite
Ca(OH)
 
2
4.FE.05Pyrochroite
Mn(OH)
 
2
4.FE.05Theophrastite
Ni(OH)
 
2
4.FE.10Bayerite
Al(OH)
 
3
4.FE.10Doyleite
Al(OH)
 
3
4.FE.10Gibbsite
Al(OH)
 
3
4.FE.10Nordstrandite
Al(OH)
 
3
4.FE.15Lepidocrocite
γ-Fe
3+
 
O(OH)
4.FE.20Grimaldiite
CrO(OH)
4.FE.20Heterogenite
CoO(OH)
4.FE.25Feitknechtite
Mn
3+
 
O(OH)
4.FE.25Lithiophorite
(Al,Li)MnO
 
2
(OH)
 
2
4.FE.30Quenselite
PbMnO
 
2
(OH)
4.FE.35Ferrihydrite
Fe
 
5
O
 
3
(OH)
 
9
4.FE.40Feroxyhyte
Fe
3+
 
O(OH)
4.FE.40Vernadite
(Mn
4+
 
,Fe
3+
 
,Ca,Na)(O,OH)
 
2
 · nH
 
2
O
4.FE.45Quetzalcoatlite
Zn
 
6
Cu
 
3
(TeO
 
6
)
 
2
(OH)
 
6
·Ag
 
x
Pb
 
y
Cl
 
x+2y
Related Minerals - Hey's Index Grouping:

- +
7.6.1Corundum
Al
 
2
O
 
3
7.6.2Diaspore
AlO(OH)
7.6.4Gibbsite
Al(OH)
 
3
7.6.5Bayerite
Al(OH)
 
3
7.6.6Nordstrandite
Al(OH)
 
3
7.6.7Doyleite
Al(OH)
 
3
7.6.8Akdalaite
4Al
 
2
O
 
3
 · H
 
2
O

Other Names for Böhmite

Other Languages:
Croatian:Bemit
Danish:Böhmit
French:Boehmite
German:Böhmit
Boehmit
Italian:Boehmite
Polish:Bemit
Russian:Бемит
Serbian (Cyrillic Script):Бемит
Spanish:Boehmita
Böhmita
Ukrainian:Беміт

Other Information

Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Industrial Uses:As a constituent of bauxite an important raw material for the industrial production of aluminium.

References for Böhmite

Reference List:Böhm, J. (1925), Zeitschrift für Anorganische Chemie 149, 203.

de Lapparent (1927), Comptes Rendus 184, 1661.

American Mineralogist (1928), 13, 72.

de Lapparent (1930), Bulletin de la Société Minéralogique 53, 262.

Goldstaub (1936), Bulletin de la Société Minéralogique 59, 348.

Palache, C., Berman, H. and Frondel, C. (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, 645-646.

Deer, W. A., Howie, R. A. and Zussman, J. (1962): Rock-forming minerals, Vol. 5, Non-silicates, 111-117.

Sahama, T. G., Lehtinen, M. and Rehtijärvi, P. (1973): Natural boehmite single crystals crom Ceylon. Contr. Mineral. Petrol. 39, 171-174.

Shelley, D., Smale, D. and Tulloch, A. J. (1977): Boehmite in syenite from New Zealand. Mineralogical Magazine 41, 398-400.

Kiss, A. B., Keresztury, G., and Farkas, L. (1980): Raman and IR spectra and structure of boehmite (γ-AlOOH). Evidence for the recently discarded D 17 2h space group. Spectrochimica Acta 36A, 653-658.

Larsen, A. O. (1981): Boehmite from syenite pegmatites in the Oslo region, Norway. Mineralogical Record 12, 227-230.

Hill, R. J. (1981): Hydrogen atoms in boehmite: a single crystal X-ray diffraction and molecular orbital study. Clays and Clay Minerals 29, 435-445.

Corbató, C. E., Tettenhorst, R. T. and Christoph, G. G. (1985): Structure refinement of deuterated boehmite. Clays and Clay Minerals 33, 71-75.

Anthony, J. W. et al. (1997): Handbook of Mineralogy, Vol. 3, 70.

Internet Links for Böhmite

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    Localities for Böhmite

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