Mineral phase
IMA name
Pyrrhotite
Class
non-silicate mineral
Compound type
sulfide
Comments
magnetic, depend on the number of Fe vacancies in the crystal structure - Polytypes: -4M: Fe7S8 (monoclinic, C2/c), -5H: Fe9S10 (orthorhombic, Cmca), -6M: Fe11S12 (monoclinic, Cc), -7H: Fe9S10 (hexagonal, P6(3)/mmc), -11H: Fe10S11 (hexagonal), Troilite: FeS (hexagonal, P6(3)/mmc)
Formula
$Fe_{1-x}S \ \ \ \ $ where $x=0-0.17$
Chemical formula
Fe(1-x)S
Elemental formula
(Fe)0.83-1 S
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$Fe$ Iron element 0.83 - 1 constituent element main
$S$ Sulfur element 1 constituent element main
Composition comments
Polytypes: -4M: Fe7S8 (1-x=0.875), -5H: Fe9S10 (1-x=0.90), -6M: Fe11S12 (1-x=0.917), -7H: Fe9S10 (1-x=0.90), -11H: Fe10S11 (1-x=0.909), Troilite: FeS (1-x=1) - Common impurities: Ni, Co, Cu

Strunz

Class
sulfides - sufosalts (02)
Division
metal sulfides, M:S = 1:1 (and similar) (02.C)
Family
With Ni, Fe, Co, PGE, etc. (02.CC)
Code
02.CC.10

Dana

Major class
sulfides (II)
Class
sulfides - including selenides and tellurides (02)
Type
where Am Bn Xp, with m:p=1:1 (02.08)
Group
-Pyrrhotite- group (02.08.10)
Code
02.08.10.01
End-members
Members
  • Pyrrhotite-4M (Fe7S8 (x=0.125))
  • Pyrrhotite-5H (Fe9S10 (x=0.1))
  • Pyrrhotite-6M (Fe11S12 (x=0.083))
  • Pyrrhotite-7H (Fe9S10 (x=0.1))
  • Pyrrhotite-11H (Fe10S11 (x=0.091))
  • Troilite (FeS (x=0) (specific mineral))
Phase type
crystalline
Crystal system
monoclinic
Crystal class
prismatic
Crystal class symbol
2/m (C2h)
Crystal spacegroup
C2/c
Molar mass
78.42 - 87.91 $g/mol$
Density
4.58 - 4.65 $g/cm^3$
State NTP
solid
Refringence type
unknown
Refringence sign
unknown
Pure color
brown
Color
bronze, bronze red, dark brown
Diaphaneity
opaque
Luster
metallic