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Goethite

This page kindly sponsored by Thomas Arroll
Johann Wolfgang von Goethe
Formula:
α-Fe3+O(OH)
System:
Orthorhombic
Colour:
brownish black, ...
Hardness:
5 - 5½
Name:
Named in 1806 by Johann Georg Lenz in honor of the German poet, novelist, playwright, philosopher, politician, and geoscientist Johann Wolfgang von Goethe [(August 28, 1749 Frankfurt, Germany – March 22, 1832 Weimar, Germany]. Goethe was Chief Minister of State of Weimar. (Portions of the Goethe mineral collection are reputedly held by the Goethe Society in New York, New York, USA.)

Classification of Goethite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
4.00.

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
0 :
0 :
6.1.1.2

6 : HYDROXIDES AND OXIDES CONTAINING HYDROXYL
1 : XO(OH)
7.20.5

7 : Oxides and Hydroxides
20 : Oxides of Fe
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First Recorded Occurrence of Goethite

Year of Discovery:
1806

Occurrences of Goethite

Geological Setting:
Common weathering product, primary hydrothermal mineral, bog and marine environments.

Physical Properties of Goethite

Adamantine, Silky, Metallic, Dull
Diaphaneity (Transparency):
Opaque
Colour:
brownish black, yellow-brown, reddish brown
Streak:
yellowish brown, orange-yellow, ocher-yellow
Hardness (Mohs):
5 - 5½
Hardness (Vickers):
VHN100=667 kg/mm2
Tenacity:
Brittle
Cleavage:
Perfect
{010}; {100} less perfect.
Fracture:
Irregular/Uneven
Density:
4.27 - 4.29 g/cm3 (Measured)    4.18 g/cm3 (Calculated)

Crystallography of Goethite

Crystal System:
Orthorhombic
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Cell Parameters:
a = 4.608Å, b = 9.956Å, c = 3.0215Å
Ratio:
a:b:c = 0.463 : 1 : 0.303
Unit Cell Volume:
V 138.62 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Prismatic [001] and striated [001]; also flattened into tablets or scales on {010}. Velvety aggregates of capillary crystals to acicular [001] and long prismatic forms often radially grouped. Massive, reniform, botryoidal, stalactitic. Bladed or columnar. Compact or fibrous concretionary nodules. Oolitic.

Crystallographic forms of Goethite

Crystal Atlas:
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Click on an icon to view
Goethite no.4 - Goldschmidt (1913-1926)
Goethite no.29 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by www.smorf.nl.

Toggle
Edge Lines | Miller Indicies | Axes

Transparency
Opaque | Translucent | Transparent

View
Along a-axis | Along b-axis | Along c-axis | Start rotation | Stop rotation
X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Optical Data of Goethite

Type:
Biaxial (-)
RI values:
nα = 2.260 - 2.275 nβ = 2.393 - 2.409 nγ = 2.393 - 2.409
2V:
Calculated: 20°
Max Birefringence:
δ = 0.133 - 0.134
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Very High
Dispersion:
relatively strong r>v
Pleochroism:
Visible
Comments:
X = red b/yellow b = clear yellow
Y = red a/yellow c = brown-yellow
Z = red c/yellow a = orange-yellow

Chemical Properties of Goethite

Formula:
α-Fe3+O(OH)
Essential elements:
All elements listed in formula:
Common Impurities:
Mn

Relationship of Goethite to other Species

4.00.Microlite Group
4.00.Pyrochlore GroupA2Nb2(O,OH)6Z
4.00.Roméite Group
4.00.Písekite-(Y)(Y,As,Ca,Fe,U)(Nb,Ti,Ta)O4
4.00.UM2004-19-O:AlCeGdZr(Gd,Ce)4Al2Zr4O17
4.00.UM2004-21-O:CaFeGdZrCa2Gd4Fe5ZrO15
4.00.UM2004-27-O:GdTiGd2Ti4O11
7.20.1WüstiteFeO
7.20.2MagnetiteFe2+Fe23+O4
7.20.3MaghemiteFe23+O3
7.20.4HematiteFe2O3
7.20.6Akaganeiteβ-Fe3+O(OH,Cl)
7.20.7FeroxyhyteFe3+O(OH)
7.20.8Lepidocrociteγ-Fe3+O(OH)
7.20.9FerrihydriteFe103+O14(OH)2
7.20.10Amakinite(Fe2+,Mg)(OH)2
7.20.11MagnesioferriteMgFe23+O4
7.20.12MuskoxiteMg7Fe4O13 · 10H2O
7.20.13SrebrodolskiteCa2Fe23+O5
7.20.14HercyniteFe2+Al2O4
7.20.15BrownmilleriteCa2(Al,Fe3+)2O5

Other Names for Goethite

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.
Industrial Uses:
Iron ore

References for Goethite

Reference List:
Posnjak and Merwin (1919), American Journal of Science: 47: 311.

Spencer (1919), Mineralogical Magazine: 18: 339.

Goldzstaub (1935), Bulletin soc. min.: 58: 6.

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: 680-685.

Canadian Mineralogist (1967): 9: 122.

Internet Links for Goethite

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

Localities for Goethite

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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