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Modderite

Formula:
(Co,Fe)As
System:OrthorhombicColour:steel grey
Hardness:4
This page provides mineralogical data about Modderite.

Classification of Modderite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:2/C.19-40
Nickel-Strunz 10th (pending) edition ID:2.CC.15

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
C : Metal Sulfides, M: S = 1: 1 (and similar)
C : With Ni, Fe, Co, PGE, etc.
Hey's CIM Ref.:3.10.9

3 : Sulphides, Selenides, Tellurides, Arsenides and Bismuthides (except the arsenides, antimonides and bismuthides of Cu, Ag and Au, which are included in Section 1)
10 : Sulphides etc. of Co
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Type Occurrence of Modderite

Co-type Localities:Modderfontein Gold Mine, Johannesburg, Witwatersrand field, Gauteng Province, South Africa
Modderfontein Mine, East Rand, Witwatersrand field, Mpumalanga Province, South Africa
Year of Discovery:1923

Physical Properties of Modderite

Lustre:Metallic
Colour:steel grey
Streak:grey
Hardness (Mohs):4

Crystallography of Modderite

Crystal System:Orthorhombic
Cell Parameters:a = 3.45Å, b = 5.86Å, c = 5.29Å
Ratio:a:b:c = 0.589 : 1 : 0.903
Unit Cell Volume:V 106.95 ų (Calculated from Unit Cell)

Chemical Properties of Modderite

Formula:
(Co,Fe)As
Essential elements:As, Co
All elements listed in formula:As, Co, Fe
Common Impurities:Ni

Relationship of Modderite to other Species

Related Minerals - Nickel-Strunz Grouping):
2.CC.05Achavalite
FeSe
2.CC.05Breithauptite
NiSb
2.CC.05Freboldite
CoSe
2.CC.05Hexatestibiopanickelite
Ni(Te,Sb)
2.CC.05Kotulskite
Pd(Te,Bi)
 
1-2
2.CC.05Langisite
(Co,Ni)As ratio Co:Ni = 5:1
2.CC.05Nickeline
NiAs
2.CC.05Sederholmite
NiSe Beta-NiSe
2.CC.05Sobolevskite
PdBi
2.CC.05Stumpflite
Pt(Sb,Bi)
2.CC.05Sudburyite
(Pd,Ni)Sb
2.CC.05Jaipurite
CoS
2.CC.05Zlatogorite
NiCuSb
 
2
2.CC.05Vavřínite
Ni
 
2
SbTe
 
2
2.CC.10Pyrrhotite
Fe
 
0.83-1
S
2.CC.10Smythite
(Fe,Ni)
 
9
S
 
11
2.CC.10Troilite
FeS
2.CC.15Cherepanovite
RhAs
2.CC.15Ruthenarsenite
(Ru,Ni)As
2.CC.15Westerveldite
(Fe,Ni,Co)As
2.CC.20Millerite
NiS
2.CC.20Mäkinenite
γ-NiSe
2.CC.25Mackinawite
(Fe,Ni)
 
9
S
 
8
2.CC.30Braggite
(Pt,Pd,Ni)S
2.CC.30Cooperite
(Pt,Pd,Ni)S
2.CC.30Vysotskite
(Pd,Ni)S
Related Minerals - Hey's Index Grouping:
3.10.1Cobaltpentlandite
(Co,Ni,Fe)
 
9
S
 
8
3.10.2Linnaeite
Co
2+
 
Co
3+
2
S
 
4
3.10.3Cattierite
CoS
 
2
3.10.4Freboldite
CoSe
3.10.5Bornhardtite
Co
2+
 
Co
3+
2
Se
 
4
3.10.6Trogtalite
CoSe
 
2
3.10.7Hastite
CoSe
 
2
3.10.8Mattagamite
CoTe
 
2
3.10.10Safflorite
(Co,Fe)As
 
2
3.10.11Clinosafflorite
(Co,Fe,Ni)As
 
2
3.10.12Skutterudite
(Co,Fe,Ni)As
 
2-3
3.10.13Cobaltite
CoAsS
3.10.14Paracostibite
CoSbS
3.10.15Costibite
CoSbS
3.10.16Alloclasite
(Co
 
0.65
Fe
 
0.35
)AsS - CoAsS
3.10.17Glaucodot
(Fe
 
0.65
Co
 
0.35
)AsS - (Co
 
0.65
Fe
 
0.35
)AsS
3.10.18Carrollite
Cu(Co,Ni)
 
2
S
 
4

Other Names for Modderite

German names:
Modderit
Russian names:
Моддерит
Spanish names:
Modderita

Other Information

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 Modderite

Reference List:American Mineralogist (1978): 63: 600.

Internet Links for Modderite

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  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Search for Modderite in the Natural History Museum (London) online catalogue
  • Modderite details from Handbook of Mineralogy (PDF)
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    Localities for Modderite

    (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.
    China
     
    • Xinjiang (Xinjiang-Uygur) Autonomous Region
      • Kashi (Kashgar; Qeshqer) Prefecture
        • Shache (Yarkand; Yeken) Co.
    		Xu Yong and Zhu Xinyou (2000): Acta Geologica Sinica 74(3), 540-543.
    South Africa
     
    • Gauteng Province
      • Witwatersrand field
        • Johannesburg
    		Chem.Metall.Min.Soc.S.Africa,(1924) 24, 265
    • Mpumalanga Province
      • Witwatersrand field
        • East Rand
    		Minerals of South Africa
    Mineral and/or Locality
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