Chromite Mineral Data

Chromite Mineral Data

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General Chromite Information

Chemical Formula:

Fe++Cr2O4

Composition:

Molecular Weight = 223.84 gm

Chromium 46.46 % Cr 67.90 % Cr₂O₃

Iron 24.95 % Fe 32.10 % FeO

Oxygen 28.59 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Fe²⁺Cr₂O₄

Environment:

Cummulate mineral found in ultramafic portions of layered mafic intrusions. Common in meteorites.

IMA Status:

Valid Species (Pre-IMA) 1845

Locality:

Bastide de la Carrade, Gassin, Var, France. Link to MinDat.org Location Data.

Name Origin:

Named after its chemical composition.

Synonym:

Chrome iron ore

Chromic iron

Ferrichromite-magnetic, altered

ICSD 20819

PDF 34-140

Chromite Image

Images:

Chromite Antigorite

Comments: Chromite veins in yellow to green antigorite with picrolite, chromian antigorite and dolomite (polished section).
Location: Wood's Mine, near 'Texas', Little Britain Township, Lancaster County, Pennsylvania, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Images:

Chromite Theophrastite

Comments: Green pearly scaly theophrastite coatings on massive dark chromite.
Location: Vermion Region, near Thessaloniki, Kedriki Makedhonia, Greece. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Chromite Crystallography

Cell Dimensions:

a = 8.36, Z = 8; V = 584.28 Den(Calc)= 5.09

Crystal System:

Isometric - HexoctahedralH-M Symbol (4/m 3 2/m) Space Group: F d3m

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

By Intensity(I/I_o): 2.52(1), 1.46(0.9), 1.6(0.9),

Forms:

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Forms: [ 1 1 1]

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Crystal Structure:

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Lenaz D , Princivalle F , The Canadian Mineralogist , 43 (2005) p.1305-1314, The crystal chemistry of detrital chromian spinel from the, southeastern Alps and Outer Dinarides: The discrimination of, supplies from areas of similar tectonic setting?, Sample: CL 1

View Additional jPOWD Structure files for Chromite
[1] [10] [2] [3] [4] [5] [6] [7] [8] [9]

Physical Properties of Chromite

Cleavage:

None

Color:

Black, Brownish black.

Density:

4.5 - 5.09, Average = 4.79

Diaphaniety:

Opaque

Fracture:

Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.

Habit:

Granular - Generally occurs as anhedral to subhedral crystals in matrix.

Habit:

Massive - Granular - Common texture observed in granite and other igneous rock.

Habit:

Nuggets - Irregular lumps produced by stream transport of malleable metals.

Hardness:

5.5 - Knife Blade

Luminescence:

None.

Luster:

Metallic

Magnetism:

Naturally weak

Streak:

brown

Optical Properties of Chromite

Gladstone-Dale:

CI meas= 0.092 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= 0.145 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.22,KPDmeas= 0.2336,KC= 0.2573

Optical Data:

Isotropic, n=2.08-2.16.

RL Color:

Gray-white with a brownish tint and brownish red internal reflections.

RL Pleochroism:

None.

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Chromite in Air**
λ	R	∑ R(λ)
400 nm	13.20
420 nm	13.10
440 nm	13.00
460 nm	12.80
480 nm	12.60
500 nm	12.40
520 nm	12.20
540 nm	12.00
560 nm	11.90
580 nm	11.80
600 nm	11.70
620 nm	11.70
640 nm	11.60
660 nm	11.60
680 nm	11.60
700 nm	11.60

**Calculated Relative Intensity Colors of Chromite in Air**
Relative Intensity	0%	80%	100%	160%	240%	320%	400%	480%	560%	640%	720%	740%
R

Calculated Properties of Chromite

Electron Density:

r_electron=4.54 gm/cc
note: r_Chromite=4.80 gm/cc.

Fermion Index

Fermion Index = 0.04956
Boson Index = 0.95044

Photoelectric:

PE_Chromite= 18.28 barns/electron
U=PE_Chromite x r_electron= 83.03 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Chromite is Not Radioactive

Chromite Classification

Dana Class:

7.2.3.3 (7)Multiple Oxides

(7.2)(A+ B++)2 X4 Spinel group

(7.2.3)(Chromium subgroup)

7.2.3.1 Magnesiochromite MgCr2O4 F d3m 4/m 3 2/m

7.2.3.2 Manganochromite (Mn,Fe)(Cr,V)2O4 F d3m 4/m 3 2/m

7.2.3.3 Chromite FeCr2O4 F d3m 4/m 3 2/m

7.2.3.4 Nichromite (Ni,Co,Fe)(Cr,Fe,Al)2O4 F d3m 4/m 3 2/m

7.2.3.5 Cochromite (Co,Ni,Fe)(Cr,Al)2O4 F d3m 4/m 3 2/m

7.2.3.6 Zincochromite ZnCr2O4 F d3m 4/m 3 2/m

Strunz Class:

IV/B.03-20 IV - Oxides

IV/B - Oxides with metal : oxygen = 3:4 (spinel type M3O4 and related) Chromite-Spinels

IV/B.03 - Spinel group, Magnesio-chromite - Zinco-chromite series

IV/B.03-10 Magnesiochromite MgCr2O4 F d3m 4/m 3 2/m

IV/B.03-20 Chromite FeCr2O4 F d3m 4/m 3 2/m

IV/B.03-30 Manganochromite (Mn,Fe)(Cr,V)2O4 F d3m 4/m 3 2/m

IV/B.03-40 Cochromite (Co,Ni,Fe)(Cr,Al)2O4 F d3m 4/m 3 2/m

IV/B.03-50 Nichromite (Ni,Co,Fe)(Cr,Fe,Al)2O4 F d3m 4/m 3 2/m

IV/B.03-60 Zincochromite ZnCr2O4 F d3m 4/m 3 2/m

Other Chromite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic1)

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

Chromite

Fe++Cr2O4
Dana No: 7.2.3.3 Strunz No: IV/B.03-20
Locality:

Notes: