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Edgarite

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Big Photo

Kaskasnyunchorr Mt., Khibiny Massif, Kola Peninsula, Murmanskaja Oblast', Northern Region, Russia
© Knut Eldjarn

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Formula:
FeNb
 
3
S
 
6
System:HexagonalColour:Dark grey
Lustre:MetallicHardness:2 - 2½
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).

Classification of Edgarite

IMA status:Approved 1995
Strunz 8th edition ID:2/D.07-20
Nickel-Strunz 10th (pending) edition ID: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
Dana 7th edition ID:2.11.13.1
mindat.org URL:http://www.mindat.org/min-6910.html
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Type Occurrence of Edgarite

Type Locality:Kaskasnyunchorr Mt., Khibiny Massif, Kola Peninsula, Murmanskaja Oblast', Northern Region, Russia
General Appearance of Type Material:Platy inclusions in Ti-(V)-rich pyrrhotite and ferroan alabandite, and as dark gray aggregates of platy grains.
Year of Discovery:1995
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:
WurtziteRutilePyrrhotitePhlogopiteMonazite-(Ce)
MarcasiteMarcasiteCorundumAlabandite

Physical Properties of Edgarite

Lustre:Metallic
Diaphaneity (Transparency):Opaque
Colour:Dark grey
Hardness (Mohs):2 - 2½
Hardness (Vickers):VHN100=135 (5 s test time)
Density (calculated):4.99 g/cm3

Crystallography of Edgarite

Crystal System:Hexagonal
Class (H-M):6 2 2 - Trapezohedral
Space Group:P63 2 2
Cell Parameters:a = 5.771Å, c = 12.19Å
Ratio:a:c = 1 : 2.112
Unit Cell Volume:V 351.59 ų (Calculated from Unit Cell)
Z:2
Comment:Space group is probable
X-Ray Powder Diffraction:
d-spacingIntensity
6.11(80)
2.606(80)
2.096(100)
1.665(80)

Optical Data of Edgarite

Type:Anisotropic
Anisotropism:White to dark brown
Reflectivity:
8.1nmR=8.%
27.4nmR=0.2(470%
27.0nmR=9.3(546%
27.0nmR=8.5(589%
nmR=6.9(650%


Graph shows reflectance levels at different wavelengths (in nm). 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:
FeNb
 
3
S
 
6
Essential elements:Fe, Nb, S
All elements listed in formula:Fe, Nb, S
Analytical Data:
Nb(57.82)
Fe(10.12)
V(0.36)
Mn(0.10)
Ti(0.04)
S(35.86)
Empirical Formula:
(Fe
 
0.96
V
 
0.04
Mn
 
0.01
)
 
&
#931;
 
1.01
Nb
 
3.03
S
 
5.95
Common Impurities:V,Mn

Relationship of Edgarite to other Species

Related Minerals - Nickel-Strunz Grouping):

- +
2.DB.05Antimonselite
Sb
 
2
Se
 
3
2.DB.05Bismuthinite
Bi
 
2
S
 
3
2.DB.05Guanajuatite
Bi
 
2
(Se,S)
 
3
2.DB.05Metastibnite
Sb
 
2
S
 
3
2.DB.05Pääkkönenite
Sb
 
2
AsS
 
2
2.DB.05Stibnite
Sb
 
2
S
 
3
2.DB.10Ottemannite
beta Sn
 
2
S
 
3
2.DB.10Suredaite
PbSnS
 
3
2.DB.15Bowieite
(Rh,Ir,Pt)
 
2
S
 
3
2.DB.15Kashinite
(Ir,Rh)
 
2
S
 
3
2.DB.20Montbrayite
(Au,Sb)
 
2
Te
 
3
2.DB.30Tarkianite
(Cu,Fe)(Re,Mo)
 
4
S
 
8
2.DB.35Cameronite
AgCu
 
7
Te
 
10

Other Names for Edgarite

Synonyms:
IMA1995-017
Other Languages:
German:Edgarit
Russian:Эдгарит
Spanish:Edgarita

Other Information

Fluorescence in UV light:nonfluorescent
Health Warning: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:

- +
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.

Internet Links for Edgarite

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  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Edgarite details from Handbook of Mineralogy (PDF)
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    • Localities for Edgarite

    Hide Locality List
    (TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
    Russia
     
    • Northern Region
      • Murmanskaja Oblast'
        • Kola Peninsula
          • Khibiny Massif
    		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.
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