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Mackinawite

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Formula:
(Fe,Ni)9S8
Also given as (Fe,Ni)1+xS (x = 0 to 0.11).
System:
Tetragonal
Colour:
Bronze, White Gray
Lustre:
Metallic
Hardness:
Name:
Named after the discovery locality.
May be confused with valleriite.

Mackinawite may form as a metastable product of sulfidation of goethite in the CH4 atmosphere but only when CO2 is added, as shown by an experiment of Wang et al. (2015); it is followed by pyrrhotite.



Classification of Mackinawite

Approved
2.CC.25

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.
Dana 7th ed.:
2.7.2.1
2.7.2.1

2 : SULFIDES
7 : AmBnXp, with (m+n):p = 9:8
3.9.6

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

Physical Properties of Mackinawite

Metallic
Diaphaneity (Transparency):
Opaque
Colour:
Bronze, White Gray
Streak:
Black
Hardness (Mohs):
Cleavage:
Perfect
Perfect on the {001}
Density:
4.17 g/cm3 (Calculated)

Chemical Properties of Mackinawite

Formula:
(Fe,Ni)9S8

Also given as (Fe,Ni)1+xS (x = 0 to 0.11).
IMA Formula:
(Fe,Ni)1+xS (x = 0-0.07)
Elements listed in formula:
Common Impurities:
Co,Cu,Ni

Crystallography of Mackinawite

Crystal System:
Tetragonal
Class (H-M):
4/mmm (4/m 2/m 2/m) - Ditetragonal Dipyramidal
Space Group:
P4/nmm
Cell Parameters:
a = 3.67 Å, c = 5.03 Å
Ratio:
a:c = 1 : 1.371
Unit Cell Volume:
V 68 ų
Z:
2

Occurrences of Mackinawite

Type Occurrence of Mackinawite

Relationship of Mackinawite to other Species

2.CC.UM2007-26-S:CuFeIrNiPtRh(Ir,Cu,Ni,Pt,Rh,Fe)9S11
2.CC.05Achávalite(Fe,Cu)Se
2.CC.05BreithauptiteNiSb
2.CC.05FrebolditeCoSe
2.CC.05KotulskitePd(Te,Bi)
2.CC.05Langisite(Co,Ni)As
2.CC.05NickelineNiAs
2.CC.05Sederholmitebeta-NiSe
2.CC.05SobolevskitePd(Bi,Te)
2.CC.05StumpflitePt(Sb,Bi)
2.CC.05Sudburyite(Pd,Ni)Sb
2.CC.05JaipuriteCoS
2.CC.05ZlatogoriteNiCuSb2
2.CC.10PyrrhotiteFe7S8
2.CC.10Smythite(Fe,Ni)3+xS4 (x=0-0.3)
2.CC.10TroiliteFeS
2.CC.15CherepanoviteRhAs
2.CC.15Modderite(Co,Fe)As
2.CC.15Ruthenarsenite(Ru,Ni)As
2.CC.15Westerveldite(Fe,Ni,Co)As
2.CC.20MilleriteNiS
2.CC.20Mäkineniteγ-NiSe
2.CC.20UM1990-38-S:CuFeIrNiPtRh(Ni,Fe,Rh,Cu,Ir,Pt)S
2.CC.30Hexatestibiopanickelite(Pd,Ni)(Sb,Te)
2.CC.30VavříniteNi2SbTe2
2.CC.35aBraggite(Pt,Pd,Ni)S
2.CC.35bCooperitePtS
2.CC.35aVysotskite(Pd,Ni)S
3.9.1PyrrhotiteFe7S8
3.9.3PyriteFeS2
3.9.4MarcasiteFeS2
3.9.5GreigiteFe2+Fe23+S4
3.9.7Smythite(Fe,Ni)3+xS4 (x=0-0.3)
3.9.8Achávalite(Fe,Cu)Se
3.9.9FerroseliteFeSe2
3.9.10FrohbergiteFeTe2
3.9.11LöllingiteFeAs2
3.9.12ArsenopyriteFeAsS
3.9.13GudmunditeFeSbS

Other Names for Mackinawite

Name in Other Languages:

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 Mackinawite

Reference List:
American Mineralogist (1963): 48: 215.

Kouvo, Olavi, Vuorelainen, Yrjo, and Long, J.V.P. (1963): A tetragonal iron sulfide. American Mineralogist 48, 511-524.

Evans H T, Milton C, Chao E C T, Adler I, Mead C, Ingram B, Berner R A (1964): Valleriite and the new iron sulfide, mackinawite. U.S. Geological Survey Professional Paper, 475-D, 64-69.

Chemie der Erde (1981): 40: 237.

Schoonen, M.A.A., Barnes, H.L. (1991) Reaction forming pyrite and marcasite from solution II. Via FeS precursors below 100° C. Geochimica et Cosmochimica Acta: 55: 1505-1514.

Krupp, R. E. (1994): Phase relations and phase transformations between the low-temperature iron sulfides mackinawite, greigite, and smythite. European Journal of Mineralogy, 6, 265-278.

American Mineralogist (1995): 80: 188.

Lennie A R, Redfern S A T, Schofield P F, Vaughan D J (1995): Synthesis and Rietveld crystal structure refinement of mackinawite, tetragonal FeS. Mineralogical Magazine, 59, 677-683.

Wolthers, M., Van Der Gaast, S.J., and Rickard, D. (2003) The structure of disordered mackinawite. American Mineralogist 88, 2007-2015.

Wolthers, M., Charlet, L., Van Der Linde, P.R., Rickard, D., and Vamn Der Weijden, C.H. (2005) Surface chemistry of disordered mackinawite (FeS). Geochemica et Cosmochimica Acta: 69: 3469-3481.

Wang, M., Chou, I-M., Lu, W., De Vivo, B. (2015): Effects of CH4 and CO2 on the sulfidization of goethite and magnetite: an in situ Raman spectroscopic study in high-pressure capillary optical cells at room temperature. European Journal of Mineralogy: 27(2): 193-201

Internet Links for Mackinawite

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https://www.mindat.org/min-2512.html
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Localities for Mackinawite

Mineral and/or Locality  
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