Goethite Mineral Data

General Goethite Information

Chemical Formula:

Fe+++O(OH)

Composition:

Molecular Weight = 88.85 gm

Iron 62.85 % Fe 89.86 % Fe₂O₃

Hydrogen 1.13 % H 10.14 % H₂O

Oxygen 36.01 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Fe³⁺O(OH)

Environment:

Common in iron ore deposits.

IMA Status:

Valid Species (Pre-IMA) 1806

Locality:

Mesabi district, Minnesota, USA. Link to MinDat.org Location Data.

Name Origin:

Named after the German poet, J. W. Goethe (1749-1832).

Name Pronunciation:

Goethite

Synonym:

Acicular iron ore

ICSD 28247

Limonite

Needle ironstone

PDF 29-713

Goethite Image

Images:

Goethite

Comments: Stellate crystalline aggregates of acicular goethite crystals.
Location: Pribram, Bohemia, Czech Republic. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Images:

Goethite Laubmannite

Comments: Reddish brown goethite hosting radiating sprays of olive green laubmannite to 3 cm across.
Location: Buckeye Mountain, Polk County, Arkansas, USA. Scale: 10.5 x 7.5 cm.
© John Veevaert

Goethite Crystallography

Axial Ratios:

a:b:c =0.4615:1:0.3034

Cell Dimensions:

a = 4.596, b = 9.957, c = 3.021, Z = 4; V = 138.25 Den(Calc)= 4.27

Crystal System:

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

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

By Intensity(I/I_o): 4.18(1), 2.69(0.3), 2.452(0.25),

Forms:

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Forms: ( 0 1 0) ( 1 1 1) ( 1 0 0) ( 1 1 0) ( 0 1 1)

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Crystal Structure:

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Gualtieri A , Venturelli P , American Mineralogist , 84 (1999) p.895-904, In situ study of the goethite-hematite phase transformation by real time, synchrotron powder diffraction, Sample at T = 25 C

View Additional jPOWD Structure files for Goethite
[1] [2] [3] [4] [5] [6]

Physical Properties of Goethite

Cleavage:

{010} Perfect, {100} Distinct

Color:

Brown, Reddish brown, Yellowish brown, Brownish yellow, Ocher yellow.

Density:

3.3 - 4.3, Average = 3.8

Diaphaneity:

Subtranslucent to opaque

Fracture:

Hackly - Jagged, torn surfaces, (e.g. fractured metals).

Habit:

Acicular - Occurs as needle-like crystals.

Habit:

Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite)

Habit:

Reniform - "Kidney like" in shape (e.g.. hematite).

Hardness:

5-5.5 - Apatite-Knife Blade

Luminescence:

Non-fluorescent.

Luster:

Adamantine - Silky

Streak:

yellowish brown

Optical Properties of Goethite

Gladstone-Dale:

CI meas= -0.14 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= -0.014 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.322,KPDmeas= 0.3618,KC= 0.3175
Ncalc = 2.05 - 2.37

Optical Data:

Biaxial (-), a=2.26-2.275, b=2.393-2.409, g=2.398-2.515, bire=0.1380-0.2400, 2V(Calc)=20-78, 2V(Meas)=0-27. Dispersion r > v extreme.

Pleochroism (x):

yellow or colorless.

Pleochroism (y):

brownish yellow or ocher yellow.

RL Anisotrophism:

Distinct in bluish grays.

RL Color:

Gray with bluish tint with yellow, red, brown internal reflections.

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Goethite in Air**
λ	R₁	R₂		∑ R₁(λ)	∑ R₂(λ)
400 nm	17.50	19.20

420 nm

16.70

18.30

440 nm

15.90

17.40

460 nm

15.20

16.70

480 nm

14.60

16.00

500 nm

14.10

15.50

520 nm

13.70

15.00

540 nm

13.30

14.60

560 nm

13.00

14.30

580 nm

12.80

14.00

600 nm

12.50

13.70

620 nm

12.40

13.50

640 nm

12.20

13.40

660 nm

12.00

13.20

680 nm

12.00

13.10

700 nm

11.90

13.00

**Calculated Relative Intensity Colors of Goethite in Air**
Relative Intensity	0%	70%	100%	140%	210%	280%	350%	420%	490%	560%	630%	680%
R₁
R₂

Calculated Properties of Goethite

Electron Density: Bulk Density (Electron Density)=4.13 gm/cc
note: Specific Gravity of Goethite =4.27 gm/cc.

Fermion Index: Fermion Index = 0.01
Boson Index = 0.99

Photoelectric: PE_Goethite= 18.93 barns/electron
U=PE_Goethite x rElectron Density= 78.24 barns/cc.

Radioactivity: GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Goethite is Not Radioactive

Goethite Classification

Dana Class: 06.01.01.02 (06)Hydroxides and Oxides Containing Hydroxyl (06.01)where X+++O OH (06.01.01)Diaspore group (Orthorhombic, Pnma or Pnmd)

06.01.01.01 Diaspore AlO(OH) Pbnm 2/m 2/m 2/m

06.01.01.02 Goethite FeO(OH) Pbnm 2/m 2/m 2/m

06.01.01.03 Groutite MnO(OH) Pbnm 2/m 2/m 2/m

06.01.01.04 Montroseite (V,Fe,V)O(OH) Pbnm 2/m 2/m 2/m

06.01.01.05 Bracewellite CrO(OH) Pbnm 2/m 2/m 2/m

06.01.01.06 Tsumgallite! GaO(OH) Pbnm 2/m 2/m 2/m

Strunz Class: 04.FD.10 04 - OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodate 04.F - Hydroxides (without V or U) 04.FD -Hydroxides with OH, without H2O; chains of edge-sharing octahedra

04.FD.10 Bracewellite CrO(OH) Pbnm 2/m 2/m 2/m

04.FD.10 Diaspore AlO(OH) Pbnm 2/m 2/m 2/m

04.FD.10 Guyanaite CrO(OH) Pnnm 2/m 2/m 2/m

04.FD.10 Groutite MnO(OH) Pbnm 2/m 2/m 2/m

04.FD.10 Goethite FeO(OH) Pbnm 2/m 2/m 2/m

04.FD.10 Montroseite (V,Fe,V)O(OH) Pbnm 2/m 2/m 2/m

04.FD.10 Tsumgallite! GaO(OH) Pbnm 2/m 2/m 2/m

Other Goethite Information

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Print or Cut-and-Paste your Goethite Specimen Label here :

Goethite

Fe+++O(OH)
Dana No: 06.01.01.02 Strunz No: 04.FD.10
Locality:

Notes: