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Edgarite

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Kaskasnyunchorr, 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.


A 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
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Type Occurrence of Edgarite

Type Locality:Kaskasnyunchorr, 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:2000
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:
RutilePyrrhotitePhlogopiteMonazite-(Ce)Marcasite
MarcasiteCorundumAlabanditeWurtzite

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)

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
Analyical 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
German names:
Edgarit
Russian names:
Эдгарит
Spanish names:
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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    Localities for Edgarite

    (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.
    Mineral and/or Locality
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