Eskolaite Mineral Data

Eskolaite Mineral Data +

General Eskolaite Information

Chemical Formula:

Cr2O3

Composition:

Molecular Weight = 151.99 gm

Chromium 68.42 % Cr 100.00 % Cr₂O₃

Oxygen 31.58 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Cr₂O₃

Environment:

In chromium-rich termolite skarns, metaquartzites, and chlorite veins. Rare component of chondrite meteorites.

IMA Status:

Valid Species (Pre-IMA) 1958

Locality:

Outokumpu, Karelia, Finland. Link to MinDat.org Location Data.

Name Origin:

Named for Pentti Eelis Eskola (1883-1964), of the University of Helsinki, Helsinki, Finland.

Synonym:

ICSD 201102

PDF 38-1479

Eskolaite Image

Images:

Eskolaite Chalcocite

Comments: Green crystalline eskolaite on massive chalcocite.
Location: Lubelin, Poland. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Eskolaite Crystallography

Axial Ratios:

a:c = 1:2.74304

Cell Dimensions:

a = 4.958, c = 13.6, Z = 6; V = 289.52 Den(Calc)= 5.23

Crystal System:

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

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

By Intensity(I/I_o): 1.67(1), 2.67(0.97), 3.63(0.96),

Crystal Structure:

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Newnham R E , de Haan Y M , Zeitschrift fur Kristallographie , 117 (1962) p.235-237, Refinement of the alpha Al2O3, Ti2O3, V2O3 and Cr2O3 structures, Locality: synthetic

View Additional jPOWD Structure files for Eskolaite
[1]

Physical Properties of Eskolaite

Cleavage:

None

Color:

Black, Dark green.

Density:

5.18

Diaphaniety:

Opaque

Fracture:

Brittle - Uneven - Very brittle fracture producing uneven fragments.

Habit:

Hexagonal - Six-sided crystal shape in cross-section or habit.

Habit:

Platy - Sheet forms (e.g. micas).

Habit:

Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).

Hardness:

8-8.5 - Between Topaz and Chrysoberyl

Luster:

Metallic

Streak:

green

Optical Properties of Eskolaite

Dichroism (e):

emerald green.

Dichroism (w):

olive green.

Optical Data:

Uniaxial (?).

NCalc= 2.52 - from Gladstone-Dale relationship (KC = 0.29) where Ncalc=Dcalc*KC+1
NCalc= 2.5 - from Gladstone-Dale relationship (KC = 0.29) where Ncalc=Dmeas*KC+1

RL Color:

Gray with emerald green internal reflections.

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Eskolaite in Air**
λ	R	∑ R(λ)
400 nm	24.50
420 nm	23.60
440 nm	22.70
460 nm	22.10
480 nm	22.00
500 nm	21.80
520 nm	21.50
540 nm	21.00
560 nm	20.50
580 nm	20.10
600 nm	19.80
620 nm	19.70
640 nm	19.60
660 nm	19.50
680 nm	19.50
700 nm	19.50

**Calculated Relative Intensity Colors of Eskolaite in Air**
Relative Intensity	0%	50%	100%	150%	200%	250%	300%	350%	400%	440%
R

Calculated Properties of Eskolaite

Electron Density:

r_electron=4.96 gm/cc
note: r_Eskolaite=5.23 gm/cc.

Fermion Index

Fermion Index = 0.06515
Boson Index = 0.93485

Photoelectric:

PE_Eskolaite= 15.66 barns/electron
U=PE_Eskolaite x r_electron= 77.59 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Eskolaite is Not Radioactive

Eskolaite Classification

Dana Class:

4.3.1.3 (4)Simple Oxides

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

(4.3.1)Corundum-Hematite group (Rhombohedral: R3¯c)

4.3.1.1 Corundum Al2O3 R 3c 3 2/m

4.3.1.2 Hematite Fe2O3 R 3c 3 2/m

4.3.1.3 Eskolaite Cr2O3 R 3c 3 2/m

4.3.1.4 Karelianite V2O3 R 3c 3 2/m

Strunz Class:

IV/C.04-30 IV - Oxides

IV/C - Oxides with metal : oxygen = 2:3 (M2O3 and related compounds)

IV/C.04 - Hematite group

IV/C.04-10 Corundum Al2O3 R 3c 3 2/m

IV/C.04-20 Hematite Fe2O3 R 3c 3 2/m

IV/C.04-30 Eskolaite Cr2O3 R 3c 3 2/m

IV/C.04-40 Karelianite V2O3 R 3c 3 2/m

Other Eskolaite Information

References:

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

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Eskolaite

Cr2O3
Dana No: 4.3.1.3 Strunz No: IV/C.04-30
Locality:

Notes: