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Eskebornite
A valid IMA mineral species - grandfathered
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About Eskebornite
Formula:
CuFeSe2
Colour:
Brass yellow
Lustre:
Metallic
Hardness:
3 - 3½
Specific Gravity:
5.35
Crystal System:
Tetragonal
Member of:
Name:
Named for the Eskeborn adit, Tilkerode, Germany, the type locality.
Unique Identifiers
Mindat ID:
1409
Long-form identifier:
mindat:1:1:1409:6
IMA Classification of Eskebornite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Cu1+Fe3+Se2-2
First published:
1950
Type description reference:
Classification of Eskebornite
2.CB.10a
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
C : Metal Sulfides, M: S = 1: 1 (and similar)
B : With Zn, Fe, Cu, Ag, etc.
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
C : Metal Sulfides, M: S = 1: 1 (and similar)
B : With Zn, Fe, Cu, Ag, etc.
2.9.1.2
2 : SULFIDES
9 : AmBnXp, with (m+n):p = 1:1
2 : SULFIDES
9 : AmBnXp, with (m+n):p = 1:1
3.1.33
3 : Sulphides, Selenides, Tellurides, Arsenides and Bismuthides (except the arsenides, antimonides and bismuthides of Cu, Ag and Au, which are included in Section 1)
1 : Sulphides etc. of Cu
3 : Sulphides, Selenides, Tellurides, Arsenides and Bismuthides (except the arsenides, antimonides and bismuthides of Cu, Ag and Au, which are included in Section 1)
1 : Sulphides etc. of Cu
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Ebn | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Eskebornite
Metallic
Transparency:
Opaque
Colour:
Brass yellow
Comment:
Tarnishes dark brown to black
Streak:
Black
Hardness:
3 - 3½ on Mohs scale
Hardness:
VHN15=155 - 252 kg/mm2 - Vickers
Cleavage:
Perfect
on {001}
on {001}
Density:
5.35 g/cm3 (Measured) 5.44 g/cm3 (Calculated)
Optical Data of Eskebornite
Anisotropism:
Marked - yellowish to tan
Reflectivity:
| Wavelength | R1 (%) | R2 (%) |
|---|---|---|
| 400nm | 22.0% | 24.5% |
| 440nm | 26.5% | 30.1% |
| 480nm | 28.7% | 33.1% |
| 520nm | 30.4% | 35.0% |
| 560nm | 31.6% | 36.0% |
| 600nm | 32.6% | 36.4% |
| 640nm | 33.3% | 37.0% |
| 680nm | 33.8% | 38.1% |
| 700nm | 34.0% | 38.7% |
Graph shows reflectance levels at different wavelengths (in nm). Peak reflectance is 38.7%.
R1 shown in black, R2 shown in red
Colour in reflected light:
brown-yellow or cream-yellow sometimes with orange tint
Pleochroism:
Weak
Comments:
Creamy yellow to yellowish brown
Chemistry of Eskebornite
Mindat Formula:
CuFeSe2
Element Weights:
Elements listed:
Chemical Analysis
wt%
| 1 | 2 | |
|---|---|---|
| Cu | 23.0 % | 23.62 % |
| Fe | 19.7 % | 19.75 % |
| Se | 57.5 % | 55.96 % |
| Total: | 100.2 % | 99.33 % |
Empirical formulas:
| Sample ID | Empirical Formula |
|---|---|
| 1 | Cu0.99Fe0.97Se2.00 |
| 2 | Cu1.06Fe1.01Se2.00 |
Sample references:
| ID | Locality | Reference | Notes |
|---|---|---|---|
| 1 | Eagle Claims U-Cu-Se occurrence, Beaverlodge Lake area, Saskatchewan, Canada | EMPA analysis of 200 micron grain embedded in and partly replaced by umangite. | |
| 2 | Martin Lake mine, Beaverlodge Lake area, Saskatchewan, Canada | EMPA analysis of a ca 100 micron grain in umangite. |
Crystallography of Eskebornite
Crystal System:
Tetragonal
Class (H-M):
42m - Scalenohedral
Space Group:
P42c
Cell Parameters:
a = 5.518(4) Å, c = 11.048(6) Å
Ratio:
a:c = 1 : 2.002
Unit Cell V:
336.39 ų (Calculated from Unit Cell)
Z:
8
Morphology:
Thick tabular crystals to 1mm
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0014365 | Eskebornite | Delgado J M, Diaz de Delgado G, Quintero M, Woolley J C (1992) The crystal structure of copper iron selenide, CuFeSe2 Materials Research Bulletin 27 367-373 | 1992 | synthetic | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.186 Å | (100) |
| 1.951 Å | (90) |
| 1.664 Å | (80) |
| 5.52 Å | (70) |
| 1.127 Å | (70) |
| 1.380 Å | (60) |
| 2.470 Å | (50) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-? alteration and/or metamorphism | |
| 33 : Minerals deposited by hydrothermal metal-rich fluids (see also [#12]) |
Geological Setting:
Low temperature hydrothermal deposits
Type Occurrence of Eskebornite
Place of Conservation of Type Material:
The Natural History Museum, London, England, 1948,325; Harvard University, Cambridge, Massachusetts, USA, 98902.
Geological Setting of Type Material:
low-temperature hydrothermal vein deposits
Associated Minerals at Type Locality:
Other Language Names for Eskebornite
Dutch:Eskeborniet
German:Eskebornit
Russian:Эскеборнит
Simplified Chinese:硒黄铜矿
Spanish:Eskebornita
Traditional Chinese:硒黃銅礦
Relationship of Eskebornite to other Species
Member of:
Other Members of Chalcopyrite Group:
| Chalcopyrite | CuFeS2 | Tet. 42m : I42d |
| Gallite | CuGaS2 | Tet. 42m : I42d |
| Laforêtite | AgInS2 | Tet. 42m : I42d |
| Lenaite | AgFeS2 | Tet. 42m : I42d |
| Roquesite | CuInS2 | Tet. 42m : I42d |
| Shenzhuangite | NiFeS2 | Tet. 42m : I42d |
| 'Unnamed (Cu-Mn-Sn Sulphide)' | Cu2MnSnS4 |
Forms a series with:
Common Associates
Associations Based on Photo Data:
| 48 photos of Eskebornite associated with Clausthalite | PbSe |
| 41 photos of Eskebornite associated with Klockmannite | CuSe |
| 18 photos of Eskebornite associated with Umangite | Cu3Se2 |
| 9 photos of Eskebornite associated with Chalcopyrite | CuFeS2 |
| 9 photos of Eskebornite associated with Calcite | CaCO3 |
| 8 photos of Eskebornite associated with Eucairite | AgCuSe |
| 8 photos of Eskebornite associated with |
Slavkovice, Nové Město na Moravě, Žďár nad Sázavou District, Vysočina Region, Czech Republic