Edgarite
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About Edgarite
Formula:
FeNb3S6
FeNb3+2Nb4+S6
Colour:
Dark grey
Lustre:
Metallic
Hardness:
2 - 2½
Specific Gravity:
4.99 (Calculated)
Crystal System:
Hexagonal
Name:
Named after Alan D. Edgar (1935–1998), Professor of Petrology, University of Western Ontario, London, Ontario, Canada, in recognition of his contributions to the study of alkaline rocks and synthetic equivalents.
An unusual sulphide mineral that appears to have formed at a very late, or final, stage of metamorphism, after the main event of fenitization, from a highly reduced, subalkaline S-C-H-rich fluid, which may have remobilized Nb as a result of destabilization of oxide minerals (Barkov et al. 2000).
The first mineral showing chalcophile behaviour of Nb. Also the first mineral with reduced Nb cations.
The first mineral showing chalcophile behaviour of Nb. Also the first mineral with reduced Nb cations.
Classification of Edgarite
Approved
Approval Year:
1995
2/D.07-20
2.DB.25
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
D : Metal Sulfides, M: S = 3 :4 and 2:3
B : M:S = 2:3
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
D : Metal Sulfides, M: S = 3 :4 and 2:3
B : M:S = 2:3
Dana 7th ed.:
2.11.13.1
Physical Properties of Edgarite
Metallic
Transparency:
Opaque
Colour:
Dark grey
Hardness:
2 - 2½ on Mohs scale
Hardness:
VHN100=135 (5 s test time) - Vickers
Cleavage:
Perfect
basal
basal
Density:
4.99 g/cm3 (Calculated)
Optical Data of Edgarite
Type:
Anisotropic
Anisotropism:
White to dark brown
Reflectivity:
| 8.1nm | R=8.% |
| 27.4nm | R=0.2(470% |
| 27.0nm | R=9.3(546% |
| 27.0nm | R=8.5(589% |
| nm | R=6.9(650% |
Graph shows reflectance levels at different wavelengths (in nm). Top of box is 100%. Peak reflectance is 9.3(546%.
Pleochroism:
Strong
Comments:
Grey to light grey with a bluish tint
Comments:
Anisotropy strong.
Chemical Properties of Edgarite
Formula:
FeNb3S6
FeNb3+2Nb4+S6
FeNb3+2Nb4+S6
Elements listed:
Common Impurities:
V,Mn
Crystallography of Edgarite
Crystal System:
Hexagonal
Class (H-M):
6 2 2 - Trapezohedral
Space Group:
P63 2 2
Cell Parameters:
a = 5.771 Å, c = 12.19 Å
Ratio:
a:c = 1 : 2.112
Unit Cell V:
351.59 ų (Calculated from Unit Cell)
Z:
2
Comment:
Space group is probable
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 6.11 | (80) |
| 2.606 | (80) |
| 2.096 | (100) |
| 1.665 | (80) |
Type Occurrence of Edgarite
General Appearance of Type Material:
Platy inclusions in Ti-(V)-rich pyrrhotite and ferroan alabandite, and as dark gray aggregates of platy grains.
Geological Setting of Type Material:
In a feldspar-rich fenitized xenolith approximately 200m across in foyaite at the Khibina alkaline complex.
Associated Minerals at Type Locality:
Synonyms of Edgarite
Other Language Names for Edgarite
Common Associates
Associated Minerals Based on Photo Data:
| Pyrrhotite | 2 photos of Edgarite associated with Pyrrhotite on mindat.org. |
Related Minerals - Nickel-Strunz Grouping
| 2.DB.05 | Antimonselite | Sb2Se3 | Orth. mmm (2/m 2/m 2/m) |
| 2.DB.05 | Bismuthinite | Bi2S3 | Orth. mmm (2/m 2/m 2/m) |
| 2.DB.05 | Guanajuatite | Bi2Se3 | Orth. mmm (2/m 2/m 2/m) : Pnma |
| 2.DB.05 | Metastibnite | Sb2S3 | Amor. |
| 2.DB.05 | Pääkkönenite | Sb2AsS2 | Mon. 2/m : B2/m |
| 2.DB.05 | Stibnite | Sb2S3 | Orth. mmm (2/m 2/m 2/m) |
| 2.DB.10 | Ottemannite | beta Sn2S3 | |
| 2.DB.10 | Suredaite | PbSnS3 | Orth. mmm (2/m 2/m 2/m) |
| 2.DB.15 | Bowieite | (Rh,Ir,Pt)2S3 | Orth. mmm (2/m 2/m 2/m) |
| 2.DB.15 | Kashinite | (Ir,Rh)2S3 | Orth. |
| 2.DB.20 | Montbrayite | (Au,Ag,Sb,Bi,Pb)23(Te,Sb,Bi,Pb)38 | Tric. |
| 2.DB.30 | Tarkianite | (Cu,Fe)(Re,Mo)4S8 | Iso. 4 3m |
| 2.DB.35 | Cameronite | Cu5-x(Cu,Ag)3+xTe10 (x = 0.43) | Mon. 2/m : B2/b |
Fluorescence of Edgarite
nonfluorescent
Other Information
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 Edgarite
Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Barkov, A.Y., R.F. Martin, Y.P. Men'shikov, Y.E. Savchenko, Y. Thibault, and K.V.O. Laajoki (2000) Edgarite, FeNb3S6, first natural niobium-rich sulfide from the Khibina alkaline complex, Russian Far North: evidence of chalcophile behavior of Nb in a fenite. Contributions to Mineralogy and Petrology: 138: 229-236.
Journal of Physics and Chemistry of Solids: 31: 1057-1067.
Journal of Solid State Chemistry: 33: 361-369.
indi, L. & Martin, R.F. (2018): Edgarite, FeNb3S6, from the Khibina Alkaline Complex, Russia: Solution of the Crystal Structure. Canadian Mineralogist, 56, (in press); http://forum.amiminerals.it/viewtopic.php?f=5&t=14592 (2018)
Internet Links for Edgarite
mindat.org URL:
https://www.mindat.org/min-6910.html
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Localities for Edgarite
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
Russia | |
| Olga Yakovleva, I. Pekov, I. Bryzgalov, Yu. Men’shikov, V. Yapaskurt, E. Guseva, N. Korotaeva (2009) Chalcogenide Minerals in Fenitized Xenoliths in Khibiny Alkaline Complex Kola Peninsula, Russia): Diversity and Chemical Features. Fifth International Symposium Mineral Diversity Research and Preservation pp213-216 |
| Barkov, A.Y., R.F. Martin, Y.P. Men'shikov, Y.E. Savchenko, Y. Thibault, and K.V.O. Laajoki (2000) Edgarite, FeNb3S6, first natural niobium-rich sulfide from the Khibina alkaline complex, Russian Far North: evidence of chalcophile behavior of Nb in a fenite. Contributions to Mineralogy and Petrology: 138: 229-236; The Canadian Mineralogist (2000): 38: 1377-1385. |
Kaskasnyunchorr Mt., Khibiny Massif, Murmanskaya Oblast', Northern Region, Russia