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

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).


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


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)

Back to Minerals