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Gibbsite

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George Gibbs
Formula:
Al(OH)3
System:
Monoclinic
Colour:
White, light gray, light ...
Hardness:
2½ - 3
Name:
Named by John Torrey in 1822 in honor of Colonel George Gibbs [January 7, 1777 Newport, RI - August 5, 1834 Sunswick Farms, NY], of Newport, Rhode Island, USA. Gibbs was a wealthy import merchant who was a geologist and mineralogist. He helped found early scientific societies for mineralogy and geology and wrote several scientific articles on geology, mineralogy, and agriculture. He amassed the finest mineral collection in the USA up to the 1810s and the collection was eventually purchased by Yale University where it was an excellent nucleus for it research and museum collection.
Commonly as nodular white masses in laterite.

Classification of Gibbsite

Approved
4.FE.10

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
6.3.1.1

6 : HYDROXIDES AND OXIDES CONTAINING HYDROXYL
3 : X(OH)3
7.6.4

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

Year of Discovery:
1822
Geological Setting of Type Material:
Bog iron deposit.
Associated Minerals at Type Locality:

Physical Properties of Gibbsite

Vitreous, Sub-Vitreous, Pearly, Dull, Earthy
Diaphaneity (Transparency):
Transparent, Translucent
Colour:
White, light gray, light green, reddish white; reddish yellow (impure)
Comment:
Ideally white; colored by mineral mixtures
Streak:
White
Hardness (Mohs):
2½ - 3
Tenacity:
Brittle
Cleavage:
Perfect
{001}, but rarely observed because of its fine-grained nature.
Fracture:
Irregular/Uneven
Density:
2.38 - 2.42 g/cm3 (Measured)    2.44 g/cm3 (Calculated)

Crystallography of Gibbsite

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Cell Parameters:
a = 8.65Å, b = 5.07Å, c = 9.7Å
β = 94.2°
Ratio:
a:b:c = 1.706 : 1 : 1.913
Unit Cell Volume:
V 424.26 ų (Calculated from Unit Cell)
Z:
8
Morphology:
Almost always earthy and nodular; rare crystals tabular {001}, with {100} and (110} usually well-developed.
Twinning:
1. About [130] as twin axis, very common. 2. On {001}, common, usually in combination with other twin laws. 3. On {100}, uncommon. 4. Rare on {110}
Comment:
Space group P21/n
X-Ray Powder Diffraction Data:
d-spacingIntensity
4.853 (100)
4.380 (36)
4.328 (18)
2.456 (12)
2.389 (16)
2.052 (12)
1.8074 (10)
Comments:
Also ICDD 33-18 synthetic

Optical Data of Gibbsite

Type:
Biaxial (+)
RI values:
nα = 1.568 - 1.570 nβ = 1.568 - 1.570 nγ = 1.586 - 1.587
Birefringence:
0.018
Max Birefringence:
δ = 0.018
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Low
Dispersion:
r > v or r < v
Optical Extinction:
Y^c = 69° X = b
Pleochroism:
Non-pleochroic

Chemical Properties of Gibbsite

Formula:
Al(OH)3
Essential elements:
All elements listed in formula:
Common Impurities:
Fe,Ga

Relationship of Gibbsite to other Species

4.FE.05Amakinite(Fe2+,Mg)(OH)2
4.FE.05BruciteMg(OH)2
4.FE.05PortlanditeCa(OH)2
4.FE.05PyrochroiteMn(OH)2
4.FE.05TheophrastiteNi(OH)2
4.FE.10BayeriteAl(OH)3
4.FE.10DoyleiteAl(OH)3
4.FE.10NordstranditeAl(OH)3
4.FE.15BöhmiteAlO(OH)
4.FE.15Lepidocrociteγ-Fe3+O(OH)
4.FE.20GrimaldiiteCrO(OH)
4.FE.20HeterogeniteCoO(OH)
4.FE.25FeitknechtiteMn3+O(OH)
4.FE.25Lithiophorite(Al,Li)MnO2(OH)2
4.FE.30QuenselitePbMnO2(OH)
4.FE.35FerrihydriteFe103+O14(OH)2
4.FE.40FeroxyhyteFe3+O(OH)
4.FE.40Vernadite(Mn4+,Fe3+,Ca,Na)(O,OH)2 · nH2O
4.FE.45QuetzalcoatliteZn6Cu3(TeO6)2(OH)6 · AgxPbyClx+2y
7.6.1CorundumAl2O3
7.6.2BöhmiteAlO(OH)
7.6.2DiasporeAlO(OH)
7.6.5BayeriteAl(OH)3
7.6.6NordstranditeAl(OH)3
7.6.7DoyleiteAl(OH)3
7.6.8Akdalaite4Al2O3 · H2O

Other Names for Gibbsite

Name in Other Languages:
Catalan:Gibbsita
Dutch:Gibbsiet
French:Gibbsite
Italian:Gibbsite
Japanese:ギブス石
Polish:Gibbsyt
Portuguese:Gibbsita
Simplified Chinese:三水铝石
Traditional Chinese:三水鋁石
Ukrainian:Гібсит

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 Gibbsite

Reference List:
Dewey (1820), American Journal of Science: 2: 249 (as wavellite).

Torrey (1822), New York. Med. Phys. Journal: 1, no. 1: 68.

Rose (1839), Annalen der Physik, Halle, Leipzig: 48: 564 (as hydrargillite).

Megaw (1934), Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 87: 185.

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: 663-667.

Zeitschrift für Kristallographie, Supplement 4 (1991): 316.

Internet Links for Gibbsite

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

Localities for Gibbsite

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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