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Formula:   Fe0.9S   mineral photo

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Crystal:   Hexagonal  
Hardness:   3.5-4.5  
Spec. Gr.:   4.6-4.7  
Streak:   black, dark grayish  
Cleavage:   N/A  
Location:   Dal'negorsk, Promorsky Krai,

"Pyrrhotite is a common reddish-brown to brownish-bronze hexagonal mineral: Fe1-xS. It has a defect lattice in which some of the ferrous ions are lacking [hence the Fe1-xS]. Pyrrhotite is attracted by the magnet... it is usually found massive and commonly associated with pentlandite, often containing as much as 5% nickel, in which case it is mined as a valuable ore of nickel," (see Bibliography 1). The name is from the Greek word PYRRO'S (fire). Pyrrhotite occurs as a high-temperature sulfide, tends to be unstable and is often replaced by pyrite, arsenopyrite and marcasite in remarkable pseudomorphs. Fine crystals have come from Freiberg, Germany; Herja, Romania; Bottino, Italy; and at Dal'negorsk, Russia. Pyrrhotite crystals are relatively rare, most often occurring as hexagonal plates. It has a brownish-bronze color, is brittle, has a gray-black streak, is magnetic, and is a good electrical conductor.

Bibliography: 1. American Geological Institute, Glossary of Geology, 1972, pg. 508.

Svenek, Jaroslav, Minerals, 1987, pp. 56-57.

University of California, Santa Barbara—Department of Earth Science
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