Boehmite Mineral Data

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General Boehmite Information

Chemical Formula:

AlO(OH)

Composition:

Molecular Weight = 59.99 gm

Aluminum 44.98 % Al 84.98 % Al₂O₃

Hydrogen 1.68 % H 15.02 % H₂O

Oxygen 53.34 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

AlO(OH)

Environment:

Major constituent of most bauxite ores.

IMA Status:

Valid Species (Pre-IMA) 1927

Locality:

Subtropical areas (Jamaica, Surinam, Guyana, Georgia, USA. France, Hungary, Russia, Greece, Australia, and Guinea) of high rainfall where lateritic soils can develop on Al-bearing igne Link to MinDat.org Location Data.

Name Origin:

Named after the German geologist and paleontologist, J. Bohm (1857-1938).

Name Pronunciation:

Boehmite

Synonym:

Bauxite - Al ore mixture

Cliachite - colloidal Al hydroxide

Kliachite - colloidal Al hydroxide

Pseudoboehmite - colloidal böhmite

Boehmite Image

Images:

Boehmite

Comments: Crystalline boehmite in bauxite rock.
Location: Bauxite, Saline County, Arkansas, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Boehmite Crystallography

Axial Ratios:

a:b:c =0.2345:1:0.3026

Cell Dimensions:

a = 2.868, b = 12.227, c = 3.7, Z = 4; V = 129.75 Den(Calc)= 3.07

Crystal System:

Orthorhombic - DipyramidalH-M Symbol (2/m 2/m 2/m) Space Group: Amam

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 6.11(1), 3.164(0.65), 2.346(0.53),

Physical Properties of Boehmite

Cleavage:

{010} Good

Color:

White, Light yellow, Yellowish green.

Density:

3 - 3.07, Average = 3.03

Diaphaneity:

Translucent

Fracture:

Brittle - Generally displayed by glasses and most non-metallic minerals.

Habit:

Massive - Uniformly indistinguishable crystals forming large masses.

Habit:

Pistolitic - > 3mm rounded spherical grains.

Hardness:

3 - Calcite

Luster:

Vitreous - Pearly

Streak:

white

Optical Properties of Boehmite

Gladstone-Dale:

CI meas= 0.052 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= 0.063 (Fair) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2127,KPDmeas= 0.2152,KC= 0.227
Ncalc = 1.68 - 1.7

Optical Data:

Biaxial (+), a=1.646, b=1.652, g=1.661, bire=0.0150, 2V(Calc)=80, 2V(Meas)=80.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Pleochroism (z):

colorless.

Calculated Properties of Boehmite

Electron Density:

Bulk Density (Electron Density)=3.04 gm/cc
note: Specific Gravity of Boehmite =3.04 gm/cc.

Fermion Index:

Fermion Index = 0.0002585608
Boson Index = 0.9997414392

Photoelectric:

PE_Boehmite= 1.35 barns/electron
U=PE_Boehmite x rElectron Density= 4.09 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Boehmite is Not Radioactive

Boehmite Classification

Dana Class:

06.01.02.01 (06)Hydroxides and Oxides Containing Hydroxyl

(06.01)where X+++O OH

(06.01.02)Boehmite Group

06.01.02.01 Boehmite AlO(OH) Amam 2/m 2/m 2/m

06.01.02.02 Lepidocrocite FeO(OH) Amam 2/m 2/m 2/m

06.01.02.03 Guyanaite CrO(OH) Pnnm 2/m 2/m 2/m

Strunz Class:

04.FE.15 04 - OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodate

04.F - Hydroxides (without V or U)

04.FE -Hydroxides with OH, without H2O; sheets of edge-sharing octahedra

04.FE.15 Boehmite AlO(OH) Amam 2/m 2/m 2/m

04.FE.15 Lepidocrocite FeO(OH) Amam 2/m 2/m 2/m

Other Boehmite Information

References:

NAME( Dana8) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)

See Also:

Links to other databases for Boehmite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - GeoScienceWorld
5 - Google Images
6 - Google Scholar
7 - MinDAT
8 - Mineralienatlas (Deutsch)
9 - Online Mineral Museum
10 - QUT Mineral Atlas
11 - Ruff.Info
12 - University of Colorado - Mineral Structure Data
13 - WWW-MINCRYST

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Ask about Boehmite here :
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Mindat.org's Discussion Groups
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Rockhounds Discussion Group on Yahoo Groups
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Print or Cut-and-Paste your Boehmite Specimen Label here :

Boehmite

AlO(OH)
Dana No: 06.01.02.01 Strunz No: 04.FE.15
Locality:

Notes: