Troilite
A valid IMA mineral species - grandfathered
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About Troilite
Formula:
FeS
May be slightly non-stoichiometric; two meteoritic troilite have the refined formula Fe0.968S and Fe0.975S, respectivly; a third, synthetic sample has Fe0.972S (Skála et al., 2006).
Colour:
Gray brown, bronze brown (tarnished), yellow brown, light greyish brown, bronze
Lustre:
Metallic
Hardness:
3½ - 4½
Specific Gravity:
4.67 - 4.79
Crystal System:
Hexagonal
Member of:
Name:
Named after Domenico Troili (11 April 1722, Macerata, Marche, Italy – 14 February 1793, Macerata, Marche, Italy) who first noted the mineral in a meteorite that fell in 1766 at Albareto, Modena (Italy).
Troilite is the only Italian mineral whose type locality is actually a meteorite impact site. The Abbé Domenico Troili, a Jesuit, is widely credited by those who study meteorites as having written the first description of the fall of a meteorite (“Ragionamento della caduta di un sasso”, published in Modena in 1766). Troili collected reports from many eyewitnesses, closely examined the stone and detected in it small grains of a brassy mineral he called “marchesita”, which was long assumed to be pyrite, FeS2. Only one century later, the mineral was recognized to be stoichiometric iron sulphide, FeS. In honour of Troili, Gustav Rose named it troilite in 1862.
Troilite is the only Italian mineral whose type locality is actually a meteorite impact site. The Abbé Domenico Troili, a Jesuit, is widely credited by those who study meteorites as having written the first description of the fall of a meteorite (“Ragionamento della caduta di un sasso”, published in Modena in 1766). Troili collected reports from many eyewitnesses, closely examined the stone and detected in it small grains of a brassy mineral he called “marchesita”, which was long assumed to be pyrite, FeS2. Only one century later, the mineral was recognized to be stoichiometric iron sulphide, FeS. In honour of Troili, Gustav Rose named it troilite in 1862.
Dimorph of:
Pyrrhotite Group. Chemically the S-analogue of achávalite. Also chemically the Fe analogue of covellite, which has the same space group.
Troilite, a native iron protosulphide, and related to the species pyrrhotite (monoclinic or hexagonal Fe1-xS; x = 0 - 0.17; several polytypes known), and smythite (trigonal (Fe,Ni)3+xS4; x = 0-0.3).
Troilite is stoichiometric FeS, without vacancies in its atomic structure, and because of this it is non-magnetic; in contrast, magnetic pyrrhotite is iron-deficient.
Troilite is considered a grandfathered species by IMA CNMNC, though in some respect it could be considered a polytype of pyrrhotite. In fact, troilite might transform into hexagonal pyrrhotite at T <122 °C (pyrrhotite-2H polytype).
Also related to buseckite, keilite and rudashevskyite, all of which are stabilised by additional essential divalent cations.
Troilite, a native iron protosulphide, and related to the species pyrrhotite (monoclinic or hexagonal Fe1-xS; x = 0 - 0.17; several polytypes known), and smythite (trigonal (Fe,Ni)3+xS4; x = 0-0.3).
Troilite is stoichiometric FeS, without vacancies in its atomic structure, and because of this it is non-magnetic; in contrast, magnetic pyrrhotite is iron-deficient.
Troilite is considered a grandfathered species by IMA CNMNC, though in some respect it could be considered a polytype of pyrrhotite. In fact, troilite might transform into hexagonal pyrrhotite at T <122 °C (pyrrhotite-2H polytype).
Also related to buseckite, keilite and rudashevskyite, all of which are stabilised by additional essential divalent cations.
Unique Identifiers
Mindat ID:
4029
Long-form identifier:
mindat:1:1:4029:3
Similar Names
| Dreelite | A synonym of Baryte | |
| Teralite | A synonym of 'Theralite' | |
| Teruelite | A variety of Dolomite | CaMg(CO3)2 |
| Torrelite (of Thompson) | A synonym of 'Columbite' | |
| Trolleite | A valid IMA mineral species - grandfathered | Al4(PO4)3(OH)3 |
| Tyrellite | A synonym of Tyrrellite | |
| Tyrolite | A valid IMA mineral species - grandfathered | Ca2Cu9(AsO4)4(CO3)(OH)8 · 11H2O |
| Tyrolite (of Delamétherie) | A synonym of Lazulite |
IMA Classification of Troilite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Fe2+S2-
Classification of Troilite
2.CC.10
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
C : Metal Sulfides, M: S = 1: 1 (and similar)
C : With Ni, Fe, Co, PGE, etc.
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
C : Metal Sulfides, M: S = 1: 1 (and similar)
C : With Ni, Fe, Co, PGE, etc.
2.8.9.1
2 : SULFIDES
8 : AmXp, with m:p = 1:1
2 : SULFIDES
8 : AmXp, with m:p = 1:1
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Tro | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
| Tro | Kretz (1983) | Kretz, R. (1983) Symbols of rock-forming minerals. American Mineralogist, 68, 277–279. |
| Tro | Siivolam & Schmid (2007) | Siivolam, J. and Schmid, R. (2007) Recommendations by the IUGS Subcommission on the Systematics of Metamorphic Rocks: List of mineral abbreviations. Web-version 01.02.07. IUGS Commission on the Systematics in Petrology. download |
| Tro | Whitney & Evans (2010) | Whitney, D.L. and Evans, B.W. (2010) Abbreviations for names of rock-forming minerals. American Mineralogist, 95, 185–187 doi:10.2138/am.2010.3371 |
| Tro | The Canadian Mineralogist (2019) | The Canadian Mineralogist (2019) The Canadian Mineralogist list of symbols for rock- and ore-forming minerals (December 30, 2019). download |
Physical Properties of Troilite
Metallic
Transparency:
Opaque
Colour:
Gray brown, bronze brown (tarnished), yellow brown, light greyish brown, bronze
Comment:
tarnishes rapidly on exposure
Streak:
Brownish black
Hardness:
3½ - 4½ on Mohs scale
Hardness:
VHN100=250 - Vickers
Tenacity:
Brittle
Cleavage:
None Observed
Fracture:
Irregular/Uneven, Sub-Conchoidal
Density:
4.67 - 4.79 g/cm3 (Measured) 4.85 g/cm3 (Calculated)
Optical Data of Troilite
Anisotropism:
strong
Chemistry of Troilite
Mindat Formula:
FeS
May be slightly non-stoichiometric; two meteoritic troilite have the refined formula Fe0.968S and Fe0.975S, respectivly; a third, synthetic sample has Fe0.972S (Skála et al., 2006).
May be slightly non-stoichiometric; two meteoritic troilite have the refined formula Fe0.968S and Fe0.975S, respectivly; a third, synthetic sample has Fe0.972S (Skála et al., 2006).
Elements listed:
Crystallography of Troilite
Crystal System:
Hexagonal
Class (H-M):
6/mmm(6/m2/m2/m) - Dihexagonal Dipyramidal
Space Group:
P63/mmc
Setting:
P63/mmc
Cell Parameters:
a = 5.958 Å, c = 11.74 Å
Ratio:
a:c = 1 : 1.97
Unit Cell V:
361.7 ų
Z:
12
Morphology:
massive, granular
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0004160 | Troilite | Skala R, Cisarova I, Drabek M (2006) Inversion twinning in troilite American Mineralogist 91 917-921 | ![]() | 2006 | 0 | 293 | |
| 0004159 | Troilite | Skala R, Cisarova I, Drabek M (2006) Inversion twinning in troilite American Mineralogist 91 917-921 | ![]() | 2006 | 0 | 293 | |
| 0004158 | Troilite | Skala R, Cisarova I, Drabek M (2006) Inversion twinning in troilite American Mineralogist 91 917-921 | ![]() | 2006 | 0 | 293 | |
| 0009770 | Troilite | King H E, Prewitt C T (1982) High-pressure and high-temperature polymorphism of iron sulfides (FeS) Acta Crystallographica B38 1877-1887 | ![]() | 1982 | 0.0001 | 293 | |
| 0009769 | Troilite | King H E, Prewitt C T (1982) High-pressure and high-temperature polymorphism of iron sulfides (FeS) Acta Crystallographica B38 1877-1887 | ![]() | 1982 | 0.0001 | 293 | |
| 0016904 | Troilite | Bertaut F (1954) La structure de sulfure de fer _cod_database_code 1009043 Journal de Physique et du Radium 15 775-775 | 1954 | 0 | 293 | ||
| 0018055 | Troilite | Alsen N (1925) Roentgenographische Untersuchungen der Kristallstrukturen von Magnetkies, Breithauptit, Pentlandit, Millerit und verwandten Verbindungen _cod_database_code 1011180 Geologiska Foreningens i Stockholm Forhandlingar 47 19-73 | 1925 | 0 | 293 | ||
| 0009771 | Troilite | King H E, Prewitt C T (1982) High-pressure and high-temperature polymorphism of iron sulfides (FeS) Acta Crystallographica B38 1877-1887 | ![]() | 1982 | 3.33 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 5.4 Å | (20) |
| 4.74 Å | (10) |
| 2.98 Å | (40) |
| 2.66 Å | (60) |
| 2.52 Å | (10) |
| 2.14 Å | (10) |
| 2.09 Å | (100) |
| 1.923 Å | (30) |
| 1.748 Å | (10) |
| 1.719 Å | (50) |
| 1.634 Å | (30) |
| 1.595 Å | (5) |
| 1.501 Å | (5) |
| 1.4609 Å | (30) |
| 1.445 Å | (20) |
| 1.422 Å | (5) |
| 1.331 Å | (40) |
| 1.284 Å | (5) |
| 1.271 Å | (5) |
| 1.224 Å | (20) |
| 1.188 Å | (10) |
| 1.179 Å | (10) |
| 1.135 Å | (20) |
| 1.119 Å | (40) |
| 1.108 Å | (30) |
| 1.091 Å | (10) |
| 1.054 Å | (30) |
| 1.024 Å | (10) |
| 0.994 Å | (20) |
Comments:
ICDD 11-151. Troilite can be recognized in powder photographs by the presence of a 5.18 A line [or probably alternatively 5.4 A] and the absence of lines with larger spacings (Carpenter & Desborough, 1964).
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Pre-terrestrial "Ur-minerals" | >4.57 |
| 1 : Stellar atmosphere condensates | |
| Stage 1: Primary nebular phases | 4.567-4.561 |
| 4 : Primary chondrule phases | 4.566–4.561 |
| Stage 2: Planetesimal differentiation and alteration | 4.566-4.550 |
| 5 : Primary asteroid phases | 4.566–4.560 |
| 6 : Secondary asteroid phases | 4.566-4.560 |
| Stage 3a: Earth’s earliest Hadean crust | >4.50 |
| 7 : Ultramafic igneous rocks | |
| Stage 3b: Earth’s earliest hydrosphere | >4.45 |
| 15 : Black/white smoker minerals and other seafloor hydrothermal minerals | |
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 36 : Carbonatites, kimberlites, and related igneous rocks | |
| Stage 10a: Neoproterozoic oxygenation/terrestrial biosphere | <0.6 |
| 50 : Coal and/or oil shale minerals | <0.36 |
| Stage 10b: Anthropogenic minerals | <10 Ka |
| 54 : Coal and other mine fire minerals (see also #51 and #56) |
Geological Setting:
Troilite occurs in serpentine, in layered ultramafic intrusives, and in meteorites. Known terrestial occurrences of troilite are not common. Found in a great number of meteorites (also Lunar and Martian) and in planetary nebulae. Found in slags and also in pulverized coal particles after combustion. Based on observations by the Voyager spacecraft in 1979 and Galileo in 1996, troilite seems to be an important phase in the mineral composition of the model rock of Jupiter's Galilean satellites Ganymede and Callisto. Based on the observations of Viking-1 and Viking-2-XRF-soil analyses and Phobos-2 orbital γ-ray data, troilite is likely to be a common mineral in the Martian surface rocks.
Type Occurrence of Troilite
Geological Setting of Type Material:
meteorite
Synonyms of Troilite
Other Language Names for Troilite
Varieties of Troilite
| Titanian Troilite | A meteoritic troilite containing appreciable titanium. |
Relationship of Troilite to other Species
Member of:
Other Members of Pyrrhotite Group:
| Pyrrhotite | Fe1-xS | Mon. |
| Smythite | (Fe,Ni)3+xS4 (x=0-0.3) | Trig. 3m(32/m) : R3m |
Common Associates
Associations Based on Photo Data:
| 75 photos of Troilite associated with 'Kamacite' | (Fe,Ni) |
| 45 photos of Troilite associated with Taenite | (Ni,Fe) |
| 31 photos of Troilite associated with Native Iron | Fe |
| 31 photos of Troilite associated with 'Fayalite-Forsterite Series' | |
| 23 photos of Troilite associated with Goethite | Fe3+O(OH) |
| 20 photos of Troilite associated with Pyrite | FeS2 |
| 18 photos of Troilite associated with 'Glass' | |
| 17 photos of Troilite associated with Plagioclase | (Na,Ca)[(Si,Al)AlSi2]O8 |
| 14 photos of Troilite associated with Schreibersite | (Fe,Ni)3P |
| 13 photos of Troilite associated with Daubréelite | Fe2+Cr3+2S4 |
Related Minerals - Strunz-mindat Grouping
| 2.CC. | Eliopoulosite | V7S8 |
| 2.CC. | Tilkerodeite | Pd2HgSe3 |
| 2.CC. | 'UM2007-26-S:CuFeIrNiPtRh' | (Ir,Cu,Ni,Pt,Rh,Fe)9S11 |
| 2.CC. | Proxitwelvefoldite | Pd3Ni4Te8 |
| 2.CC. | Ferrotorryweiserite | Rh5Fe10S16 |
| 2.CC. | Tamuraite | Ir5Fe10S16 |
| 2.CC. | Crowningshieldite | (Ni0.9Fe0.1)S |
| 2.CC. | Kuvaevite | Ir5Ni10S16 |
| 2.CC. | Torryweiserite | Rh5Ni10S16 |
| 2.CC.05 | Achávalite | FeSe |
| 2.CC.05 | Langisite | CoAs |
| 2.CC.05 | Sederholmite | NiSe |
| 2.CC.05 | Freboldite | CoSe |
| 2.CC.05 | Nickeline | NiAs |
| 2.CC.05 | Sobolevskite | PdBi |
| 2.CC.05 | Jaipurite | CoS |
| 2.CC.05 | Kotulskite | Pd(Te,Bi)2-x (x ≈ 0.4) |
| 2.CC.05 | Zlatogorite | NiCuSb2 |
| 2.CC.05 | Stumpflite | PtSb |
| 2.CC.05 | Sudburyite | PdSb |
| 2.CC.05 | Breithauptite | NiSb |
| 2.CC.10 | Pyrrhotite | Fe1-xS |
| 2.CC.10 | Smythite | (Fe,Ni)3+xS4 (x=0-0.3) |
| 2.CC.15 | Ruthenarsenite | (Ru,Ni)As |
| 2.CC.15 | Westerveldite | (Fe,Ni,Co)As |
| 2.CC.15 | Modderite | CoAs |
| 2.CC.15 | Minakawaite | RhSb |
| 2.CC.15 | Cherepanovite | RhAs |
| 2.CC.20 | 'UM1990-38-S:CuFeIrNiPtRh' | (Ni,Fe,Rh,Cu,Ir,Pt)S |
| 2.CC.20 | Millerite | NiS |
| 2.CC.20 | Mäkinenite | NiSe |
| 2.CC.25 | Mackinawite | FeS |
| 2.CC.30 | Vavřínite | Ni2SbTe2 |
| 2.CC.30 | 'Hexatestibiopanickelite' | (Pd,Ni)(Sb,Te) ? |
| 2.CC.35b | Cooperite | PtS |
| 2.CC.35a | Vysotskite | PdS |
| 2.CC.35a | Braggite | PdPt3S4 |
| 2.CC.45 | Jacutingaite | Pt2HgSe3 |
| 2.CC.50 | 'Imgreite' | NiTe (?) |
Other Information
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Troilite in petrology
An essential component of rock names highlighted in red, an accessory component in rock names highlighted in green.
Internet Links for Troilite
mindat.org URL:
https://www.mindat.org/min-4029.html
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References for Troilite
Reference List:
Carpenter, Robert Heron, Desborough, George A. (1964) Range in solid solution and structure of naturally occurring troilite and pyrrhotite. American Mineralogist, 49 (9-10) 1350-1365
Carpenter, Robert H., Bailey, and Arthur C. (1973) Application of Ro and At measurements to the study of pyrrhotite and troilite. American Mineralogist, 58 (5-6) 440-443
King, H. E., Prewitt, C. T. (1982) High-pressure and high-temperature polymorphism of iron sulfide (FeS) Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry, 38 (7) 1877-1887 doi:10.1107/s0567740882007523
Töpel-Schadt, Jutta, Müller, Wolfgang Friedrich (1982) Transmission electron microscopy on meteoritic troilite. Physics and Chemistry of Minerals, 8 (4). 175-179 doi:10.1007/bf00308240
Bennett, Marvin E., McSween, Harry Y. (1996) Shock features in iron-nickel metal and troilite of L-group ordinary chondrites. Meteoritics & Planetary Science, 31 (2) 255-264 doi:10.1111/j.1945-5100.1996.tb02021.x
Marvin, Ursula B., Cosmo, Mario L. (2002) Domenico Troili (1766): “The true cause of the fall of a stone in Albereto is a subterranean explosion that hurled the stone skyward”. Meteoritics & Planetary Science, 37 (12) 1857-1864 doi:10.1111/j.1945-5100.2002.tb01169.x
Thomas, Joan E, Skinner, William M, Smart, Roger S.t.C (2003) A comparison of the dissolution behavior of troilite with other iron(II) sulfides; implications of structure. Geochimica et Cosmochimica Acta, 67 (5) 831-843 doi:10.1016/s0016-7037(02)01146-8
Tenailleau, C.; Etschmann, B.; Wang, H.; Pring, A.; Grguric, B. A.; Studer, A. (2005) Thermal expansion of troilite and pyrrhotite determined by in situ cooling (873 to 373 K) neutron powder diffraction measurements. Mineralogical Magazine, 69 (2). 205-216 doi:10.1180/0026461056920247
Ono, S., Kikegawa, T. (2006) High-pressure study of FeS, between 20 and 120 GPa, using synchrotron X-ray powder diffraction. American Mineralogist, 91 (11) 1941-1944 doi:10.2138/am.2006.2347
Skála, Roman; Císařová, Ivana; Drábek, Milan (2006) Inversion twinning in troilite. American Mineralogist, 91 (5). p.917-921. doi:10.2138/am.2006.1999
Tan, Zheng, Su, Xuping, Li, Zhi, Liu, Ya, Wang, Jianhua (2007) Phase equilibria in the Zn–Fe–S system at 450°C. International Journal of Materials Research, 98 (1) 16-20 doi:10.3139/146.101435
Avril, Caroline, Malavergne, Valérie, Caracas, Razvan, Zanda, Brigitte, Reynard, Bruno, Charon, Emeline, Bobocioiu, Ema, Brunet, Fabrice, Borensztajn, Stephan, Pont, Sylvain, et al. (2013) Raman spectroscopic properties and Raman identification of CaS‐MgS‐MnS‐FeS‐Cr2FeS4 sulfides in meteorites and reduced sulfur‐rich systems. Meteoritics & Planetary Science, 48 (8). 1415-1426 doi:10.1111/maps.12145
Localities for Troilite
Showing 1,226 localities.
Locality List
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All localities listed without proper references should be considered as questionable.
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Takhtarvumchorr Mt, Murmansk Oblast, Russia