Ferrihydrite Mineral Data

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General Ferrihydrite Information

Chemical Formula:

Fe+++2O3•0.5(H2O)

Composition:

Molecular Weight = 168.70 gm

Iron 66.21 % Fe 94.66 % Fe₂O₃

Hydrogen 0.60 % H 5.34 % H₂O

Oxygen 33.19 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Fe³⁺₂O₃•0.5(H₂O)

Environment:

Secondary mineral in an oxidizing environment, strongly dependant on pH.

IMA Status:

Approved IMA 1973

Locality:

Clara mine, Grube Clara, Germany Link to MinDat.org Location Data.

Name Origin:

Named for the composition as a hydrated ferric iron compound.

Name Pronunciation:

Ferrihydrite

Ferrihydrite Image

Images:

Ferrihydrite

Comments: Brown ferrihydrite.
Location: Fischersdorf, near Saalfeld, Thuringia, Germany. Scale: Picture size 6 mm.
© Thomas Witzke

Ferrihydrite Crystallography

Axial Ratios:

a:c = 1:3.17567

Cell Dimensions:

a = 2.96, c = 9.4, Z = 1; V = 71.33 Den(Calc)= 3.93

Crystal System:

Trigonal - Hexagonal ScalenohedralH-M Symbol (3 2/m) Space Group: P 31c

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

By Intensity(I/I_o): 2.45(1), 1.97(0.6), 2.25(0.6),

Crystal Structure:

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Jansen E , Kyek A , Schafer W , Schwertmann U , Applied Physics , A74 (2002) p.S1004-S1006, The structure of six-line ferrihydrite, Locality: synthetic, Sample: defect-free refinement

Physical Properties of Ferrihydrite

Color:

Yellow brown, Dark brown.

Density:

3.8

Habit:

Aggregates - Made of numerous individual crystals or clusters.

Habit:

Microscopic Crystals - Crystals visible only with microscopes.

Streak:

yellowish brown

Optical Properties of Ferrihydrite

Optical Data:

NCalc= 2.24 - from Gladstone-Dale relationship (KC = 0.3163) where Ncalc=Dcalc*KC+1
NCalc= 2.2 - from Gladstone-Dale relationship (KC = 0.3163) where Ncalc=Dmeas*KC+1

Calculated Properties of Ferrihydrite

Electron Density:

Bulk Density (Electron Density)=3.77 gm/cc
note: Specific Gravity of Ferrihydrite =3.93 gm/cc.

Fermion Index:

Fermion Index = 0.01
Boson Index = 0.99

Photoelectric:

PE_Ferrihydrite= 20.08 barns/electron
U=PE_Ferrihydrite x rElectron Density= 75.77 barns/cc.

Radioactivity:

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

Ferrihydrite Classification

Dana Class:

04.03.02.02 (04)Simple Oxides

(04.03)with a cation charge of 3+ (A+++2 O3)

(04.03.02)Dana Group

04.03.02.01 Akdalaite 5(Al2O3)•(H2O) P 6₃mc 6mm

04.03.02.02 Ferrihydrite Fe2O3•0.5(H2O) P 31c 3 2/m

Strunz Class:

04.FE.35 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.35 Ferrihydrite Fe2O3•0.5(H2O) P 31c 3 2/m

Other Ferrihydrite Information

References:

PHYS. PROP.(Enc. of Minerals,2nd ed.,1990)

See Also:

Links to other databases for Ferrihydrite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info

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

Ferrihydrite

Fe+++2O3•0.5(H2O)
Dana No: 04.03.02.02 Strunz No: 04.FE.35
Locality:

Notes: