Troilite

Troilite
Polished and etched surface of the Mundrabilla meteorite from Australia. The darker brownish areas with striations are troilite with exolved daubréelite.
General
CategorySulfide mineral
Formula
(repeating unit)
FeS
IMA symbolTro[1]
Strunz classification2.CC.10
Crystal systemHexagonal
Crystal classDitrigonal dipyramidal (6m2)
H-M symbol: (6m2)
Space groupP62c
Unit cella = 5.958, c = 11.74 [Å]; Z = 12
Identification
ColorPale gray brown
Crystal habitMassive, granular; nodular; platey to tabular
CleavageNone
FractureIrregular
Mohs scale hardness3.5–4.0
LusterMetallic
StreakGray black
DiaphaneityOpaque
Specific gravity4.67–4.79
Alters toTarnishes on exposure to air
References[2][3][4]

Troilite (/ˈtrɔɪlt/) is a rare iron sulfide mineral with the simple formula of FeS. It is the iron-rich endmember of the pyrrhotite group. Pyrrhotite has the formula Fe(1-x)S (x = 0 to 0.2) which is iron deficient. As troilite lacks the iron deficiency which gives pyrrhotite its characteristic magnetism, troilite is non-magnetic.[3]

Troilite can be found as a native mineral on Earth but is more abundant in meteorites, in particular, those originating from the Moon and Mars. It is among the minerals found in samples of the meteorite that struck Russia in Chelyabinsk on February 15th, 2013.[5] Uniform presence of troilite on the Moon and possibly on Mars has been confirmed by the Apollo, Viking and Phobos space probes. The relative intensities of isotopes of sulfur are rather constant in meteorites as compared to the Earth minerals, and therefore troilite from Canyon Diablo meteorite is chosen as the international sulfur isotope ratio standard, the Canyon Diablo Troilite (CDT).

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Handbook of Mineralogy
  3. ^ a b Troilite on Mindat.org
  4. ^ Troilite on Webmineral
  5. ^ Chappell, Bill (22 February 2013). "Attack By Chondrite: Scientists ID Russian Meteor". NPR. npr.org. Retrieved 2013-02-22.