Mineral - Pyrrhotite
Pyrrhotite
Chemical Properties
Mineral Class
Sulfides and sulfosalts
Toxicity
none
Formula
Fe₇S₈
Unit Cell
a=6.87 b=11.90 c=22.72 β=91° Z=64
Physical Properties
Hardness
3.5 - 4.5
Streak
gray
Density
Heavy (3,5-6)
Cleavage
Distinct after {0001}
Fracture
conchoidal
Tenacity
Brittle
Optical Properties
Color
browngraybronze
Birefringence
Luster
Metallic
Transparency
opaque
Pleochroism
Geomineralogical Properties
Crystal System
monoclinic
Point Group
monoclinic-prismatic - 2/m
Space Group
C2/c (15)
Habit
leafy, prismatic, pyramidal, tabular
Formation
(1) Magmatic, resulting from the segregation of a sulfide melt from mafic to ultramafic magmas.
(2) Metamorphic and metasomatic, resulting from the thermal transformation of pyrite.
(3) In hydrothermal veins under reducing conditions.
Paragenesis
Twinning
Anchor-shaped contact twins after {10 1 2}
Rarity
Common
Synonyms
Pyrrhotite
Composition
Elements
Mass
Fe
60.18
S
39.82
South Dakota (Palache et al. 1952)
Groups and Members
Pyrrhotite-Group