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Lepidocrocite

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Formula:
γ-Fe3+O(OH)
Colour:
Deep red, red-brown
Lustre:
Sub-Metallic
Hardness:
5
Specific Gravity:
4.05 - 4.13
Crystal System:
Orthorhombic
Name:
From the Greek λεπίς, scale, and κροκη, thread, in allusion to the occasional palmate or plumose aggregates.
Dimorphous with Goethite.

May be a component of limonite.

The red inclusions in many quartz crystals, often labelled by sellers as "lepidocrocite", are in fact normally hematite. We are unaware of any analytically confirmed red translucent scaly lepidocrocite as inclusions in quartz crystals. Likewise, colourfully iridescent mammillary "turgite" crusts are sometimes sold as "lepidocrocite" but are usually goethite.


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Classification of LepidocrociteHide

Approved, 'Grandfathered' (first described prior to 1959)
4.FE.15

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
6.1.2.2

6 : HYDROXIDES AND OXIDES CONTAINING HYDROXYL
1 : XO(OH)
7.20.8

7 : Oxides and Hydroxides
20 : Oxides of Fe

Physical Properties of LepidocrociteHide

Sub-Metallic
Transparency:
Transparent
Colour:
Deep red, red-brown
Streak:
Orange
Hardness:
Tenacity:
Brittle
Cleavage:
Perfect
{010}; {100} less perfect; {001} good.
Density:
4.05 - 4.13 g/cm3 (Measured)    3.96 g/cm3 (Calculated)

Optical Data of LepidocrociteHide

Type:
Biaxial (-)
RI values:
nα = 1.940 nβ = 2.200 nγ = 2.510
2V:
Measured: 83° , Calculated: 84°
Max Birefringence:
δ = 0.570
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Very High
Type:
Anisotropic
Anisotropism:
Strong
Dispersion:
relatively weak
Colour in reflected light:
Gray-white
Pleochroism:
Strong
Comments:
X = b = clear yellow
Y = c = dark red-orange
Z = a = darker red-orange

Chemical Properties of LepidocrociteHide

Formula:
γ-Fe3+O(OH)
IMA Formula:
Fe3+O(OH)
Common Impurities:
Mn

Crystallography of LepidocrociteHide

Crystal System:
Orthorhombic
Class (H-M):
mm2 - Pyramidal
Space Group:
Cmc21
Cell Parameters:
a = 3.07 Å, b = 12.54 Å, c = 3.88 Å
Ratio:
a:b:c = 0.245 : 1 : 0.309
Unit Cell V:
149.37 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Flattened scales {010} and slightly elongated [100]. {010} sometimes striated [100]. Single crystals attached by an edge to matrix; aggregated into palmate or plumose groups. Loose rosettes; massive, bladed to fibrous or micaceous. Fibrous varieties elongated [100].

X-Ray Powder DiffractionHide

Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.
Powder Diffraction Data:
d-spacingIntensity
6.26 (100)
3.29 (90)
2.47 (80)
1.937 (70)
1.732 (40)
1.524 (40)
1.075 (40)

Type Occurrence of LepidocrociteHide

Synonyms of LepidocrociteHide

Other Language Names for LepidocrociteHide

Varieties of LepidocrociteHide

HydrolepidocrociteLepidocrocite with adsorbed water.

Common AssociatesHide

Associated Minerals Based on Photo Data:
Goethite40 photos of Lepidocrocite associated with Goethite on mindat.org.
Amethyst21 photos of Lepidocrocite associated with Amethyst on mindat.org.
Quartz21 photos of Lepidocrocite associated with Quartz on mindat.org.
Malachite10 photos of Lepidocrocite associated with Malachite on mindat.org.
Azurite9 photos of Lepidocrocite associated with Azurite on mindat.org.
Murdochite7 photos of Lepidocrocite associated with Murdochite on mindat.org.
Dolomite6 photos of Lepidocrocite associated with Dolomite on mindat.org.
Pyrolusite5 photos of Lepidocrocite associated with Pyrolusite on mindat.org.
Hematite5 photos of Lepidocrocite associated with Hematite on mindat.org.
Limonite5 photos of Lepidocrocite associated with Limonite on mindat.org.

Related Minerals - Nickel-Strunz GroupingHide

4.FE.05Amakinite(Fe2+,Mg)(OH)2Trig.
4.FE.05BruciteMg(OH)2Trig. 3m (3 2/m) : P3m1
4.FE.05PortlanditeCa(OH)2Trig. 3m (3 2/m)
4.FE.05PyrochroiteMn(OH)2Trig. 3m (3 2/m)
4.FE.05TheophrastiteNi(OH)2Trig. 3m (3 2/m) : P3m1
4.FE.10BayeriteAl(OH)3Mon. 2/m : P21/m
4.FE.10DoyleiteAl(OH)3Tric.
4.FE.10GibbsiteAl(OH)3Mon. 2/m
4.FE.10NordstranditeAl(OH)3Tric. 1 : P1
4.FE.15BöhmiteAlO(OH)Orth. mmm (2/m 2/m 2/m)
4.FE.20GrimaldiiteCrO(OH)Trig.
4.FE.20HeterogeniteCo3+O(OH)Hex.
4.FE.25FeitknechtiteMn3+O(OH)Trig. 3m (3 2/m) : P3m1
4.FE.25Lithiophorite(Al,Li)MnO2(OH)2Trig. 3m (3 2/m) : R3m
4.FE.30QuenselitePbMnO2(OH)Mon. 2/m : P2/b
4.FE.35FerrihydriteFe3+10O14(OH)2Trig.
4.FE.40FeroxyhyteFe3+O(OH)Hex.
4.FE.40Vernadite(Mn4+,Fe3+,Ca,Na)(O,OH)2 · nH2OHex.
4.FE.45QuetzalcoatliteZn6Cu3(TeO6)2(OH)6 · AgxPbyClx+2yTrig. 3m (3 2/m) : P3m1

Related Minerals - Dana Grouping (8th Ed.)Hide

6.1.2.1BöhmiteAlO(OH)Orth. mmm (2/m 2/m 2/m)
6.1.2.3GuyanaiteCrO(OH)Orth.

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

7.20.1WüstiteFeOIso. m3m (4/m 3 2/m) : Fm3m
7.20.2MagnetiteFe2+Fe3+2O4Iso. m3m (4/m 3 2/m) : Fd3m
7.20.3MaghemiteFe3+2O3Iso. 4 3 2 : P41 3 2
7.20.4HematiteFe2O3Trig. 3m (3 2/m) : R3c
7.20.5Goethiteα-Fe3+O(OH)Orth. mmm (2/m 2/m 2/m)
7.20.6Akaganeite(Fe3+,Ni2+)8(OH,O)16Cl1.25 · nH2OMon. 2/m
7.20.7FeroxyhyteFe3+O(OH)Hex.
7.20.9FerrihydriteFe3+10O14(OH)2Trig.
7.20.10Amakinite(Fe2+,Mg)(OH)2Trig.
7.20.11MagnesioferriteMgFe3+2O4Iso. m3m (4/m 3 2/m) : Fd3m
7.20.12MuskoxiteMg7Fe4O13 · 10H2OTrig. 3m (3 2/m)
7.20.13SrebrodolskiteCa2Fe3+2O5Orth. mmm (2/m 2/m 2/m) : Pnma
7.20.14HercyniteFe2+Al2O4Iso. m3m (4/m 3 2/m) : Fd3m
7.20.15BrownmilleriteCa2(Al,Fe3+)2O5Orth. mm2

Other InformationHide

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 LepidocrociteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Posnjak, E., Merwin, H.E. (1919) The hydrated ferric oxides. American Journal of Science: 47: 311-348.
Palache, C., Berman, H., Frondel, C. (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: 642-645.
(1978) Acta Chemica Scandinavica: A: 87.

Internet Links for LepidocrociteHide

Localities for LepidocrociteHide

This 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.

Locality ListShow

Mineral and/or Locality  
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