Formula: FeS
Sulphide, pyrrhotite group
Crystal System: Hexagonal
Specific gravity: 4.67 to 4.79 measured, 4.85 calculated
Hardness: 3½ to 4½
Streak: Brownish black
Colour: Grey brown, bronze brown (tarnished), yellow brown, light greyish brown, bronze
Environments
Plutonic igneous environments rare
Meteorites common
Troilite occurs in serpentine, in layered
ultramafic plutonic igneous rocks and in meteorites (AES, Webmin).
Terrestrial occurrences are rare, but it is found in many meteorites, Lunar and Martian rocks and in planetary nebulae
(AES).
In meteorites troilite is associated with daubreelite,
chromite, sphalerite,
graphite, and various phosphates and silicates
(HOM).
Localities
At the Wannaway deposit, Widgiemooltha, Coolgardie Shire, Western Australia, troilite is associated with
pyrrhotite, pentlandite,
mackinawite, cubanite,
valleriite and chalcopyrite
(HOM).
At the Sally Malay deposit, Halls Creek Shire, Western Australia, troilite occurs with
iron-copper-nickel sulphides in
a layered ultramafic intrusion (HOM).
The type locality is the Albareto meteorite, Modena Province, Emilia-Romagna, Italy; troilite is the only Italian
mineral whose type locality is actually a meteorite impact site (Mindat).
Troilite from the Albareto Meteorite - Image
The Abee enstatite - chondrodite
meteorite landed near Abee, Alberta, Canada; in it troilite is associated with
keilite
(Minrec 35.4.353).
At Disko Island, Qeqertalik, Greenland, Denmark, troilite occurs with native iron in
basalt
(Dana).
Troilite from Disko Island - Image
At the Palitra pegmatite, Lovozero Massif, Murmansk Oblast, Russia, troilite occurs as grains to 1 mm in aggregates of
bartonite and chlorbartonite
(Minrec 36.5.412).
At Del Norte county, California, USA, troilite occurs in serpentine
(HOM).
Troilite from Del Norte County - Image
Alteration
chalcopyrite, arsenopyrite and
pyrite to Fe-tennantite and
troilite
10CuFeS2 + 4FeAsS + FeS2 → Cu10Fe2As4S13 + 13FeS
(CM 28.725-738)
chalcopyrite, arsenopyrite and
sulphur to Fe-tennantite and
troilite
l0CuFeS2 + 4FeAsS + l/2S2 → Cu10Fe2As4S13 + l2FeS
(CM 28.725-738)
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