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Pyrrhotite

This page kindly sponsored by Eugene Standifer
Formula:
Fe7S8
Also given as Fe1-x (x = 0 to 0.17).
System:
Monoclinic
Colour:
Bronze brown, bronze ...
Lustre:
Metallic
Hardness:
3½ - 4
Name:
Named in 1847 by Ours Pierre Armand Petit Dufrenoy from Greek πνρρός "pyrrhos", flame-colored.
Pyrrhotite Group.

Pyrrhotite is found with pentlandite in basic igneous rocks, veins and metamorphic rocks. It is also often found with pyrite, marcasite and magnetite. It has varying magnetic powers, depending on the number of Fe vacancies in the crystal structure. A related species with no vacancies (and therefore non-magnetic), is called troilite and has been found in meteorites and rarely terrestrially.

Visually similar to smythite.

Classification of Pyrrhotite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
2.CC.10

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.
2.8.10.1

2 : SULFIDES
8 : AmXp, with m:p = 1:1
3.9.1

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
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Physical Properties of Pyrrhotite

Metallic
Diaphaneity (Transparency):
Opaque
Colour:
Bronze brown, bronze red, or dark brown
Comment:
Tarnishes quickly
Streak:
Dark grayish black
Hardness (Mohs):
3½ - 4
Hardness (Vickers):
VHN100=373 - 409 kg/mm2
Cleavage:
None Observed
Parting:
Distinct on {0001}
Fracture:
Sub-Conchoidal
Density:
4.58 - 4.65 g/cm3 (Measured)    4.69 g/cm3 (Calculated)

Crystallography of Pyrrhotite

Polytype:
Formula:
Crystal System:
Class (H-M)
Space Group:
Space Group Setting:
Cell Parameters:
Ratio:
Unit Cell Volume (calc):
Z:
Pyrrhotite-11HPyrrhotite-4MPyrrhotite-5CPyrrhotite-6CPyrrhotite-6MPyrrhotite-7H
Fe10S11Fe7S8Fe9S10Fe11S12Fe11S12Fe9S10
Hexagonal Monoclinic Monoclinic Monoclinic Monoclinic Hexagonal 
2/m - Prismatic2 - Sphenoidalm - Domatic
 B2/b P21 Bb   
 C2/c P21 Cc   

a = 11.88Å, b = 6.87Å, c = 22.79Å
β = 90.47°
a = 6.8673(4) Å, b = 28.6536(9) Å, c = 6.8592(4) Å
β = 119.975(7)°
a = 6.8973(15) Å, b = 11.954(3) Å, c = 17.602(4) Å
α = 90°, β = 101.302(4)°, γ = 90°


 a:b:c = 1.729 : 1 : 3.317a:b:c = 0.24 : 1 : 0.239a:b:c = 0.577 : 1 : 1.472  
 V 1,859.96 ų
(Calculated from Unit Cell)
V 1169.18 ųV 1423.1 ų  
  44  

Crystallographic forms of Pyrrhotite

Crystal Atlas:
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Pyrrhotite no.15 - Goldschmidt (1913-1926)
Pyrrhotite - {101}, {001}
Pyrrhotite - {100}, {001}
Pyrrhotite - Contact twin on {10-12}
3d models and HTML5 code kindly provided by www.smorf.nl.

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Edge Lines | Miller Indicies | Axes

Transparency
Opaque | Translucent | Transparent

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Along a-axis | Along b-axis | Along c-axis | Start rotation | Stop rotation

Epitaxial Relationships of Pyrrhotite

Epitaxial Minerals:
Epitaxy Comments:
Usually the pyrrhotite is on the galena, but codepositing intergrowths are known. The "six-fold" axis of pyrrhotite is parallel to the three-fold axis (octahedral axis) in galena.
X-Ray Powder Diffraction Data:
d-spacingIntensity
3.00 (4)
2.65 (6)
2.08 (10)
1.728 (5)
1.328 (4)
1.105 (4)
1.052 (3)

Optical Data of Pyrrhotite

Type:
Anisotropic
Anisotropism:
Strong
Pleochroism:
Weak

Chemical Properties of Pyrrhotite

Formula:
Fe7S8

Also given as Fe1-x (x = 0 to 0.17).
Essential elements:
All elements listed in formula:
Common Impurities:
Ni,Co,Cu

Relationship of Pyrrhotite to other Species

Structurally related to group(s):
2.CC.UM2007-26-S:CuFeIrNiPtRh(Ir,Cu,Ni,Pt,Rh,Fe)9S11
2.CC.05Achavalite(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.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(Ir,Pt,Ni,Fe)S
2.CC.25Mackinawite(Fe,Ni)9S8
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
3.9.3PyriteFeS2
3.9.4MarcasiteFeS2
3.9.5GreigiteFe2+Fe23+S4
3.9.6Mackinawite(Fe,Ni)9S8
3.9.7Smythite(Fe,Ni)3+xS4 (x=0-0.3)
3.9.8Achavalite(Fe,Cu)Se
3.9.9FerroseliteFeSe2
3.9.10FrohbergiteFeTe2
3.9.11LöllingiteFeAs2
3.9.12ArsenopyriteFeAsS
3.9.13GudmunditeFeSbS

Other Names for Pyrrhotite

Name in Other Languages:
Basque:Pirrotita
Catalan:Pirrotina
Czech:Pyrhotin
French:Pyrrhotite
Italian:Pirrotite
Japanese:磁硫鉄鉱
Lithuanian:Pirotinas
Norwegian (Bokmål):Magnetkis
Polish:Pirotyn
Portuguese:Pirrotite
Simplified Chinese:磁黄铁矿
Slovak:Pyrotit
Swedish:Magnetkis
Traditional Chinese:磁黃鐵礦
Ukrainian:Піротин

Other Information

Other Information:
Variably magnetic
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 Pyrrhotite

Reference List:
Palache, Charles, Harry Berman & Clifford Frondel (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged, 834pp.: 231-235.

Kiskyras, D. A. (1950): The magnetic properties of pyrrhotite at various temperatures with special regard to its origin. Neues Jahrbuch für Mineralogie, Geologie und Paläontologie, Abhandlungen, Abteilung A: Mineralogie, Petrographie 80A, 297-342.

Carpenter, R. H. & Desborough, G. A. (1964): Range in solid solution and structure of naturally occurring troilite and pyrrhotite. Am. Mineral. 49, l350-1365.

R. G. Arnold (1967): Range in composition and structure of 82 natural terrestrial pyrrhotites. Can. Mineral. 9, 31-50.

M. E. Fleet and N. MacRae (1969): Two-phase hexagonal pyrrhotites. Can. Mineral. 9, 699-705.

A. R. Graham (1969): Quantitative determination of hexagonal and monoclinic pyrrhotites by X-ray diffraction. Can. Mineral. 10, 4-24.

Clark, A. H. (1970): Quantitative determination of hexagonal and monoclinic pyrrhotites by X-ray diffraction: A discussion. Canadian Mineralogist, 10, 278-280.

Yund, R.A. & H.T. Hall (1970): Kinetics and mechanism of pyrite exsolution from pyrrhotite. Journal of Petrology 11: 381-404.

Fleet, M.E. (1971): The crystal structure of a pyrrhotite (Fe7S8). Acta Crystallographica: B27: 1864-1867.

Batt, A. P. (1972) Shorter communications: Nickel distribution in hexagonal and monoclinic pyrrhotite. Canadian Mineralogist, 11, 892-897.

Carpenter, H.R. & A.C. Bailey (1973): Application of Ro and Ar measurements to the study of pyrrhotite and troilite. American Mineralogy 58: 440-443.

Ramsden, A. R. (1975): Compositions of coexisting pyrrhotites, pentlandites and pyrites at Spargoville, western Australia. Canadian Mineralogist, 13, 133-137.

Morimoto, N., Gyobu, A., Mukaiyama, H., and Izawa, E. (1975): Crystallography and stability of pyrrhotites. Economic Geology, 70, 824-833.

Corlett, M. (1977): Iron oxides and pyrrhotites from Igdlukunguaq, Disko Island, Greenland. Canadian Mineralogist, 15, 540-545.

Fleet, M. E. (1978): The pyrrhotite - marcasite transformation. Canadian Mineralogist, 16, 31-35.

King, H. E., Jnr and Prewitt, C. T. (1982): High-pressure and high-temperature polymorphism of iron sulfide (FeS). Acta Crystallographica B38, 1877-1887. [doi:10.1107/S0567740882007523]

Campbell, F. A. & Ethier, V. G. (1984): Nickel and cobalt in pyrrhotite and pyrite from the Faro and Sullivan orebodies. Canadian Mineralogist, 22, 503-506.

Pasquariello, D. M., Kershaw, R., Passaretti, J. D., Dwight, K., Wold, A. (1984): Low-temperature synthesis and properties of Co9S8, Ni3S2, and Fe7S8, Inorganic Chemistry, 23, 872-874.

Keller-Besrest, F., Collin, G. (1990): Structural aspects of the α transition in stoichiometric FeS: identification of the high-temperature phase. Journal of Solid State Chemistry, 84, 194-210.

Barkov, A. Y., Laajoki, K. V. O., Men'shikov, Y. P., Alapieti, T. T., Sivonen, S. J. (1997): First terrestrial occurrence of titanium-rich pyrrhotite, marcasite and pyrite in a fenitized xenolith from the Khibina alkaline complex, Russia. Canadian Mineralogist, 35, 875-885.

Nesbitt, H.W., Schaufuss, A.G., Scaini, M., Bancroft, G.M., and Szargan, R. (2001) XPS measurement of fivefold and six-fold coordinated sulfur in pyrrhotites and evidence for millerite and pyrrhotite surface species. American Mineralogist: 86: 318-326.

Farrell, S. P., Fleet, M. E. (2002): Phase separation in (Fe,Co)1-xS monosulfide solid-solution below 450°C, with consequences for coexisting pyrrhotite and pentlandite in magmatic sulfide deposits. Canadian Mineralogist, 40, 33-46.

Froese, E. (2003): Point defects in pyrrhotite. Canadian Mineralogist, 41, 1061-1067.

Selivanov, E.N., Vershinin, A.D., and Gulyaeva, R.I. (2003) Thermal expansion of troilite and pyrrhotine in helium and air. Inorganic Materials: 39: 1097-1102.

Powell, A.V., Vaqueiro, P., Knight, K.S., Chapon, L.C. & Sanchez, R.D. (2004): Structure and magnetism in synthetic pyrrhotite Fe7S8: a powder neutron-diffraction study. Phys. Rev., Serie 3.B - Condensed Matter 70, 014415-1 - 014415-12.

Wang, H., Salveson, I. (2005): A review on the mineral chemistry of the non-stoichiometric iron sulphide, Fe1-xS (0≤x≤0.125): polymorphs, phase relations and transitions, electronic and magnetic structures. Phase Transitions, 78, 547-567.

de Villiers, J. P. R., Liles, D. C. (2010): The crystal-structure and vacancy distribution in 6C pyrrhotite. American Mineralogist, 95, 148-152.

Becker, M., de Villiers, J. and Bradshaw, D. (2010): The Mineralogy and Crystallography of Pyrrhotite from Selected Nickel and PGE Ore Deposits. Economic Geology, 105, 1025-1037.

Harries, D., Pollok, K. & Langenhorst, F. (2011): Translation interface modulation in NC-pyrrhotites: Direct imaging by TEM and a model toward understanding partially disordered structural states. American Mineralogist, 96, 716-731.

Lilies, D. C., Villiers, J. P. R. D. (2012): Redetermination of the structure of 5C pyrrhotite at low temperature and at room temperature. American Mineralogist, 97, 257-261.

Internet Links for Pyrrhotite

Specimens:
The following Pyrrhotite specimens are currently listed for sale on minfind.com.

Localities for Pyrrhotite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
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