Pyrrhotite

Pyrrhotite

General
Category	Mineral
iron sulfide:Fe_1-xS (x = 0 to 0.2)
Identification
Color	Bronze
Crystal habit	Tabular or prismatic in hexagonal prisms; massive to granular
monoclinic, 2/m
Cleavage	Absent
Fracture	Uneven
Mohs Scale hardness	3.5 - 4.5
Luster	Metallic
Refractive index	Opaque
Streak	Dark grey - black
Specific gravity	4.6
Fusibility	3
hydrochloric acid
Other Characteristics	Weakly magnetic, strongly magnetic on heating

Pyrrhotite is an unusual magnetism increases as the iron content decreases.

Pyrrhotite is odd also because it has two crystal symmetries. When pyrrhotite is high in iron and the formula is closer to true FeS the structure is hexagonal. But, when it is low in iron, the structure is monoclinic. Both symmetries occur together in the same specimen.

The name is derived from Greek pyrrhos, flame-colored.

Pyrrhotite is a rather common trace constituent of igneous rocks. It occurs as segregation deposits from metamorphic zones.

The troilite endmember, though only rarely encountered in the Earth's crust, is found in many meteorites. One iron meteorite, Mundrabilla, contains 25 to 35 volume percent troilite.^[1]

References and external links

Dana's Manual of Mineralogy ISBN 0-471-03288-3
Mineral Galleries: Pyrrhotite
Webmineral.com
Mindat.org

^ Vagn Buchwald, Handbook of Iron Meteorites, 1975.

Categories: Iron minerals

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Pyrrhotite". A list of authors is available in Wikipedia.