Gibbsite Mineral Data

Gibbsite Mineral Data +

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General Gibbsite Information

Chemical Formula:

Al(OH)3

Composition:

Molecular Weight = 78.00 gm

Aluminum 34.59 % Al 65.36 % Al₂O₃

Hydrogen 3.88 % H 34.64 % H₂O

Oxygen 61.53 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Al(OH)₃

Environment:

Lateritic soils developed on aluminous rocks in areas of high rainfall.

IMA Status:

Valid Species (Pre-IMA) 1822

Locality:

Bauxite deposits of Arkansas, USA. Link to MinDat.org Location Data.

Name Origin:

Named after the American collector, G. Gibbs (1776-1833).

Synonym:

Hydrargyllite

ICSD 36233

PDF 33-18

Gibbsite Image

Images:

Gibbsite

Comments: Transparent to white, tabular-prismatic gibbsite crystals.
Location: Saga Quarry, Langesundfjord, Oslo Region, Norway. Scale: Crystal size 1 mm.
© John Veevaert

Images:

Gibbsite Doyleite

Comments: Botryoidal spheres of doyleite growing along with its dimorph gibbsite. Analysis shows that doyleite dominates the mix. There are also minor canary yellow phlogopite crystals.
Location: Baoshan, Yunnan, China. Scale: 8 x 6.5 x 1.9 cm.
© Fabre Minerals

Gibbsite Crystallography

Axial Ratios:

a:b:c =1.7043:1:1.9169

Cell Dimensions:

a = 8.641, b = 5.07, c = 9.719, Z = 8; beta = 94.566° V = 424.44 Den(Calc)= 2.44

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: P 2₁/n

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

By Intensity(I/I_o): 4.82(1), 4.34(0.4), 4.3(0.2),

Crystal Structure:

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Balan E , Lazzeri M , Morin G , Mauri F , American Mineralogist , 91 (2006) p.115-119, First-principles study of the OH-stretching modes of gibbsite, Locality: hypothetical structure calculated with DFT

View Additional jPOWD Structure files for Gibbsite
[1]

Physical Properties of Gibbsite

Cleavage:

[001] Perfect

Color:

Bluish, Green, Green white, Gray, Gray white.

Density:

2.3 - 2.4, Average = 2.34

Diaphaniety:

Translucent to transparent

Fracture:

Tough - Difficult to break apart as shown by fibrous minerals and most metals.

Habit:

Earthy - Dull, clay-like texture with no visible crystalline affinities, (e.g. howlite).

Habit:

Spherical - Spherical, rounded aggregates.

Habit:

Stalactitic - Shaped like pendant columns as stalactites or stalagmites (e.g. calcite).

Hardness:

2.5-3 - Finger Nail-Calcite

Luminescence:

None.

Luster:

Vitreous - Pearly

Streak:

white

Optical Properties of Gibbsite

Gladstone-Dale:

CI meas= 0.033 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= 0.069 (Fair) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2356,KPDmeas= 0.2446,KC= 0.2531

Optical Data:

Biaxial (+), a=1.568-1.57, b=1.568-1.57, g=1.586-1.587, bire=0.0170-0.0180, 2V(Calc)=0, 2V(Meas)=0-5. Dispersion r > v or r < v.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Pleochroism (z):

colorless.

Calculated Properties of Gibbsite

Electron Density:

r_electron=2.41 gm/cc
note: r_Gibbsite=2.35 gm/cc.

Fermion Index

Fermion Index = 0.0003
Boson Index = 0.9997

Photoelectric:

PE_Gibbsite= 1.10 barns/electron
U=PE_Gibbsite x r_electron= 2.65 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Gibbsite is Not Radioactive

Gibbsite Classification

Dana Class:

6.3.1.1 (6)Hydroxides and Oxides Containing Hydroxyl

(6.3)with (OH)3 or (OH)6 groups

(6.3.1)Dana Group

6.3.1.1 Gibbsite Al(OH)3 P 2₁/n 2/m

Strunz Class:

IV/F.02-10 IV - Oxides

IV/F - Hydroxides and oxidic hydrates, water-bearing oxides with layered structure

IV/F.02 - Gibbsite - Doyleite series

IV/F.02-10 Gibbsite Al(OH)3 P 2₁/n 2/m

IV/F.02-20 Bayerite Al(OH)3 P 2₁/a 2/m

IV/F.02-30 Nordstrandite Al(OH)3 P1 1

IV/F.02-40 Doyleite Al(OH)3 P1 1

Other Gibbsite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)

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Gibbsite

Al(OH)3
Dana No: 6.3.1.1 Strunz No: IV/F.02-10
Locality:

Notes: