Cochromite Mineral Data

Cochromite Mineral Data

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General Cochromite Information

Chemical Formula:

(Co,Ni,Fe++)(Cr,Al)2O4

Composition:

Molecular Weight = 207.97 gm

Magnesium 1.17 % Mg 1.94 % MgO

Aluminum 5.19 % Al 9.81 % Al₂O₃

Chromium 35.00 % Cr 51.16 % Cr₂O₃

Iron 8.06 % Fe 6.91 % FeO / 3.84 % Fe₂O₃

Cobalt 14.17 % Co 18.01 % CoO

Nickel 5.64 % Ni 7.18 % NiO

Oxygen 30.77 % O

______ ______

100.00 % 98.85 % = TOTAL OXIDE

Empirical Formula:

Co_0.5Ni_0.2Fe²⁺_0.2Mg_0.1Cr_1.4Al_0.4Fe³⁺_0.1O₄

Environment:

Replacing chromite in a small tabular nickel deposit in a contact between quartzite and serpentinized ultramafics.

IMA Status:

Approved IMA 1978

Locality:

Bon Accord deposit, Barberton, Transvaal, South Africa. Link to MinDat.org Location Data.

Name Origin:

Named for a chromite with essential cobalt.

Synonym:

ICSD 69503

PDF 22-1084

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Cochromite Crystallography

Cell Dimensions:

a = 8.292, Z = 8; V = 570.14 Den(Calc)= 4.85

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): 2.512(1), 1.4721(0.45), 2.947(0.35),

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Physical Properties of Cochromite

Cleavage:

[???] Indistinct

Color:

Black.

Density:

5.22

Diaphaniety:

Opaque

Fracture:

Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).

Habit:

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

Hardness:

7 - Quartz

Luster:

Metallic

Streak:

green

Optical Properties of Cochromite

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Cochromite in Air**
λ	R	∑ R(λ)
480 nm	14.30
546 nm	13.70
589 nm	14.00
656 nm	13.90

**Calculated Relative Intensity Colors of Cochromite in Air**
Relative Intensity	0%	70%	100%	140%	210%	280%	350%	420%	490%	560%	630%
R

Calculated Properties of Cochromite

Electron Density:

r_electron=4.61 gm/cc
note: r_Cochromite=4.85 gm/cc.

Fermion Index

Fermion Index = 0.03691
Boson Index = 0.96309

Photoelectric:

PE_Cochromite= 17.80 barns/electron
U=PE_Cochromite x r_electron= 82.11 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Cochromite is Not Radioactive

Cochromite Classification

Dana Class:

7.2.3.5 (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.03-40 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 Cochromite Information

References:

NAME( AntBidBlaNic3) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic3)

See Also:

Links to other databases for Cochromite :
1 -Am. Min. Crystal Structure Database 2 -Athena 3 - EUROmin Project 4 -Google Images 5 -Google Scholar 6 -Handbook of Mineralogy (UofA) 7 -MinDAT 8 -MinMax(Deutsch) 9 -MinMax(English) 10 -Mineralienatlas (Deutsch) 11 -QUT Mineral Atlas 12 - WWW-MINCRYST 13 -École des Mines de Paris

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Cochromite

(Co,Ni,Fe++)(Cr,Al)2O4
Dana No: 7.2.3.5 Strunz No: IV/B.03-40
Locality:

Notes: