Troilite

Last updated
Troilite
Mundrabilla.jpg
Polished and etched surface of the Mundrabilla meteorite from Australia. The darker brownish areas with striations are troilite with exolved daubréelite.
General
Category Sulfide mineral
Formula
(repeating unit)
FeS
IMA symbol Tro [1]
Strunz classification 2.CC.10
Crystal system Hexagonal
Crystal class Ditrigonal dipyramidal (6m2)
H-M symbol: (6m2)
Space group P62c
Unit cell a = 5.958, c = 11.74 [Å]; Z = 12
Identification
ColorPale gray brown
Crystal habit Massive, granular; nodular; platey to tabular
Cleavage None
Fracture Irregular
Mohs scale hardness3.5–4.0
Luster Metallic
Streak Gray black
Diaphaneity Opaque
Specific gravity 4.67–4.79
Alters toTarnishes on exposure to air
References [2] [3] [4]

Troilite 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]

Contents

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).

Structure

Troilite has hexagonal structure (Pearson symbol hP24, Space group P-62c No 190). Its unit cell is approximately a combination of two vertically stacked basic NiAs-type cells of pyrrhotite, where the top cell is diagonally shifted. [6] For this reason, troilite is sometimes called pyrrhotite-2C. [7]

Discovery

A meteorite fall was observed in 1766 at Albareto, Modena, Italy. Samples were collected and studied by Domenico Troili who described the iron sulfide inclusions in the meteorite. These iron sulfides were long considered to be pyrite (i.e., FeS2). In 1862, German mineralogist Gustav Rose analyzed the material and recognized it as stoichiometric 1:1 FeS and gave it the name troilite in recognition of the work of Domenico Troili. [2] [3] [8]

Occurrence

Troilite has been reported from a variety of meteorites occurring with daubréelite, chromite, sphalerite, graphite, and a variety of phosphate and silicate minerals. [2] It has also been reported from serpentinite in the Alta mine, Del Norte County, California, and in layered igneous intrusions in Western Australia, the Ilimaussaq intrusion of southern Greenland, the Bushveld Complex in South Africa and at Nordfjellmark, Norway. In the South African and Australian occurrence it is associated with copper, nickel, platinum iron ore deposits occurring with pyrrhotite, pentlandite, mackinawite, cubanite, valleriite, chalcopyrite and pyrite. [2] [9]

Troilite is extremely rarely encountered in the Earth's crust (even pyrrhotite is relatively rare compared to pyrite and Iron(II) sulfate minerals). Most troilite on Earth is of meteoritic origin. One iron meteorite, Mundrabilla contains 25 to 35 volume percent troilite. [10] The most famous troilite-containing meteorite is Canyon Diablo. Canyon Diablo Troilite (CDT) is used as a standard of relative concentration of different isotopes of sulfur. [11] Meteoritic standard was chosen because of the constancy of the sulfur isotopic ratio in meteorites, whereas the sulfur isotopic composition in Earth materials varies due to the bacterial activity. In particular, certain sulfate reducing bacteria can reduce 32
SO2−
4
1.07 times faster than 34
SO2−
4
, which may increase the 34
S
/32
S
ratio by up to 10%. [12]

Troilite is the most common sulfide mineral at the lunar surface. It forms about one percent of the lunar crust and is present in any rock or meteorite originating from moon. In particular, all basalts brought by the Apollo 11, 12, 15 and 16 missions contain about 1% of troilite. [6] [13] [14] [15]

Troilite is regularly found in Martian meteorites (i.e. those originating from Mars). Similar to the Moon's surface and meteorites, the fraction of troilite in Martian meteorites is close to 1%. [16] [17]

Based on observations by the Voyager spacecraft in 1979 and Galileo in 1996, troilite might also be present in the rocks of Jupiter’s satellites Ganymede and Callisto. [18] Whereas experimental data for Jupiter's moons are yet very limited, the theoretical modeling assumes large percentage of troilite (~22.5%) in the core of those moons. [19]

See also

Related Research Articles

<span class="mw-page-title-main">Basalt</span> Magnesium- and iron-rich extrusive igneous rock

Basalt is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed at or very near the surface of a rocky planet or moon. More than 90% of all volcanic rock on Earth is basalt. Rapid-cooling, fine-grained basalt is chemically equivalent to slow-cooling, coarse-grained gabbro. The eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Basalt is also an important rock type on other planetary bodies in the Solar System. For example, the bulk of the plains of Venus, which cover ~80% of the surface, are basaltic; the lunar maria are plains of flood-basaltic lava flows; and basalt is a common rock on the surface of Mars.

<span class="mw-page-title-main">Pyrite</span> Iron (II) disulfide mineral

The mineral pyrite ( PY-ryte), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula FeS2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral.

<span class="mw-page-title-main">Pentlandite</span> Iron–nickel sulfide

Pentlandite is an iron–nickel sulfide with the chemical formula (Fe,Ni)9S8. Pentlandite has a narrow variation range in nickel to iron ratios (Ni:Fe), but it is usually described as 1:1. In some cases, this ratio is skewed by the presence of pyrrhotite inclusions. It also contains minor cobalt, usually at low levels as a fraction of weight.

<span class="mw-page-title-main">Anorthosite</span> Mafic intrusive igneous rock composed predominantly of plagioclase

Anorthosite is a phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90–100%), with a minimal mafic component (0–10%). Pyroxene, ilmenite, magnetite, and olivine are the mafic minerals most commonly present.

<span class="mw-page-title-main">Pyrrhotite</span> Magnetic iron sulfide mineral

Pyrrhotite is an iron sulfide mineral with the formula Fe(1-x)S. It is a nonstoichiometric variant of FeS, the mineral known as troilite. Pyrrhotite is also called magnetic pyrite, because the color is similar to pyrite and it is weakly magnetic. The magnetism decreases as the iron content decreases, and troilite is non-magnetic. Pyrrhotite is generally tabular and brassy/bronze in color with a metallic luster. The mineral occurs with mafic igneous rocks like norites, and may form from pyrite during metamorphic processes. Pyrrhotite is associated and mined with other sulfide minerals like pentlandite, pyrite, chalcopyrite, and magnetite, and has been found globally.

<span class="mw-page-title-main">Marcasite</span> Iron disulfide (FeS2) with orthorhombic crystal structure

The mineral marcasite, sometimes called "white iron pyrite", is iron sulfide (FeS2) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Both structures contain the disulfide S22− ion, having a short bonding distance between the sulfur atoms. The structures differ in how these di-anions are arranged around the Fe2+ cations. Marcasite is lighter and more brittle than pyrite. Specimens of marcasite often crumble and break up due to the unstable crystal structure.

<span class="mw-page-title-main">Canyon Diablo (meteorite)</span> Iron meteorite from Meteor Crater used as sulfur isotopic reference material

The Canyon Diablo meteorite refers to the many fragments of the asteroid that created Meteor Crater, Arizona, United States. Meteorites have been found around the crater rim, and are named for nearby Canyon Diablo, which lies about three to four miles west of the crater.

Iron sulfide or Iron sulphide can refer to range of chemical compounds composed of iron and sulfur.

<span class="mw-page-title-main">Sulfur cycle</span> Biogeochemical cycle of sulfur

The important sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. It is important in geology as it affects many minerals and in life because sulfur is an essential element (CHNOPS), being a constituent of many proteins and cofactors, and sulfur compounds can be used as oxidants or reductants in microbial respiration. The global sulfur cycle involves the transformations of sulfur species through different oxidation states, which play an important role in both geological and biological processes. Steps of the sulfur cycle are:

<span class="mw-page-title-main">Pyroxferroite</span>

Pyroxferroite (Fe2+,Ca)SiO3 is a single chain inosilicate. It is mostly composed of iron, silicon and oxygen, with smaller fractions of calcium and several other metals. Together with armalcolite and tranquillityite, it is one of the three minerals which were discovered on the Moon during the 1969 Apollo 11 mission. It was then found in Lunar and Martian meteorites as well as a mineral in the Earth's crust. Pyroxferroite can also be produced by annealing synthetic clinopyroxene at high pressures and temperatures. The mineral is metastable and gradually decomposes at ambient conditions, but this process can take billions of years.

<span class="mw-page-title-main">Mineral redox buffer</span>

In geology, a redox buffer is an assemblage of minerals or compounds that constrains oxygen fugacity as a function of temperature. Knowledge of the redox conditions (or equivalently, oxygen fugacities) at which a rock forms and evolves can be important for interpreting the rock history. Iron, sulfur, and manganese are three of the relatively abundant elements in the Earth's crust that occur in more than one oxidation state. For instance, iron, the fourth most abundant element in the crust, exists as native iron, ferrous iron (Fe2+), and ferric iron (Fe3+). The redox state of a rock affects the relative proportions of the oxidation states of these elements and hence may determine both the minerals present and their compositions. If a rock contains pure minerals that constitute a redox buffer, then the oxygen fugacity of equilibration is defined by one of the curves in the accompanying fugacity-temperature diagram.

<span class="mw-page-title-main">Mackinawite</span> Iron nickel sulfide mineral

Mackinawite is an iron nickel sulfide mineral with the chemical formula (Fe,Ni)
1+x
S
. The mineral crystallizes in the tetragonal crystal system and has been described as a distorted, close packed, cubic array of S atoms with some of the gaps filled with Fe. Mackinawite occurs as opaque bronze to grey-white tabular crystals and anhedral masses. It has a Mohs hardness of 2.5 and a specific gravity of 4.17. It was first described in 1962 for an occurrence in the Mackinaw mine, Snohomish County, Washington for which it was named.

<span class="mw-page-title-main">Cubanite</span> Copper iron sulfide mineral

Cubanite is a copper iron sulfide mineral that commonly occurs as a minor alteration mineral in magmatic sulfide deposits. It has the chemical formula CuFe2S3 and when found, it has a bronze to brass-yellow appearance. On the Mohs hardness scale, cubanite falls between 3.5 and 4 and has a orthorhombic crystal system. Cubanite is chemically similar to chalcopyrite; however, it is the less common copper iron sulfide mineral due to crystallization requirements.

Tranquillityite is silicate mineral with formula (Fe2+)8Ti3Zr2 Si3O24. It is mostly composed of iron, oxygen, silicon, zirconium and titanium with smaller fractions of yttrium and calcium. It is named after the Mare Tranquillitatis (Sea of Tranquility), the place on the Moon where the rock samples were found during the 1969 Apollo 11 mission. It was the last mineral brought from the Moon which was thought to be unique, with no counterpart on Earth, until it was discovered in Australia in 2011.

<span class="mw-page-title-main">Composition of Mars</span> Branch of the geology of Mars

The composition of Mars covers the branch of the geology of Mars that describes the make-up of the planet Mars.

<span class="mw-page-title-main">Northwest Africa 7034</span> Martian meteorite

Northwest Africa 7034 is a Martian meteorite believed to be the second oldest yet discovered. It is estimated to be two billion years old and contains the most water of any Martian meteorite found on Earth. Although it is from Mars it does not fit into any of the three SNC meteorite categories, and forms a new Martian meteorite group named "Martian ". Nicknamed "Black Beauty", it was purchased in Morocco and a slice of it was donated to the University of New Mexico by its American owner. The image of the original NWA 7034 was photographed in 2012 by Carl Agee, University of New Mexico.

<span class="mw-page-title-main">Carlsbergite</span> Chromium nitride mineral found in meteorites

Carlsbergite is a nitride mineral that has the chemical formula CrN, or chromium nitride.

The δ34S value is a standardized method for reporting measurements of the ratio of two stable isotopes of sulfur, 34S:32S, in a sample against the equivalent ratio in a known reference standard. Presently, the most commonly used standard is Vienna-Canyon Diablo Troilite (VCDT). Results are reported as variations from the standard ratio in parts per thousand, per mil or per mille, using the ‰ symbol. Heavy and light sulfur isotopes fractionate at different rates and the resulting δ34S values, recorded in marine sulfate or sedimentary sulfides, have been studied and interpreted as records of the changing sulfur cycle throughout the earth's history.

Astropedology is the study of very ancient paleosols and meteorites relevant to the origin of life and different planetary soil systems. It is a branch of soil science (pedology) concerned with soils of the distant geologic past and of other planetary bodies to understand our place in the universe. A geologic definition of soil is “a material at the surface of a planetary body modified in place by physical, chemical or biological processes”. Soils are sometimes defined by biological activity but can also be defined as planetary surfaces altered in place by biologic, chemical, or physical processes. By this definition, the question for Martian soils and paleosols becomes, were they alive? Astropedology symposia are a new focus for scientific meetings on soil science. Advancements in understanding the chemical and physical mechanisms of pedogenesis on other planetary bodies in part led the Soil Science Society of America (SSSA) in 2017 to update the definition of soil to: "The layer(s) of generally loose mineral and/or organic material that are affected by physical, chemical, and/or biological processes at or near the planetary surface and usually hold liquids, gases, and biota and support plants". Despite our meager understanding of extraterrestrial soils, their diversity may raise the question of how we might classify them, or formally compare them with our Earth-based soils. One option is to simply use our present soil classification schemes, in which case many extraterrestrial soils would be Entisols in the United States Soil Taxonomy (ST) or Regosols in the World Reference Base for Soil Resources (WRB). However, applying an Earth-based system to such dissimilar settings is debatable. Another option is to distinguish the (largely) biotic Earth from the abiotic Solar System, and include all non-Earth soils in a new Order or Reference Group, which might be tentatively called Astrosols.

Sulfur isotope biogeochemistry is the study of the distribution of sulfur isotopes in biological and geological materials. In addition to its common isotope, 32S, sulfur has three rare stable isotopes: 34S, 36S, and 33S. The distribution of these isotopes in the environment is controlled by many biochemical and physical processes, including biological metabolisms, mineral formation processes, and atmospheric chemistry. Measuring the abundance of sulfur stable isotopes in natural materials, like bacterial cultures, minerals, or seawater, can reveal information about these processes both in the modern environment and over Earth history.

References

  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. 1 2 3 4 Handbook of Mineralogy
  3. 1 2 3 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.
  6. 1 2 Evans, Ht Jr. (Jan 1970). "Lunar Troilite: Crystallography". Science. 167 (3918): 621–623. Bibcode:1970Sci...167..621E. doi:10.1126/science.167.3918.621. ISSN   0036-8075. PMID   17781520. S2CID   8047914.
  7. Hubert Lloyd Barnes (1997). Geochemistry of hydrothermal ore deposits. John Wiley and Sons. pp. 382–390. ISBN   0-471-57144-X.
  8. Gerald Joseph Home McCall; A. J. Bowden; Richard John Howarth (2006). The history of meteoritics and key meteorite collections. Geological Society. pp. 206–207. ISBN   1-86239-194-7.
  9. Kawohl, A; Frimmel, H.E. (2016). "Isoferroplatinum-pyrrhotite-troilite intergrowth as evidence of desulfurization in the Merensky Reef at Rustenburg (western Bushveld Complex, South Africa)". Mineralogical Magazine. 80 (6): 1041–1053. Bibcode:2016MinM...80.1041K. doi:10.1180/minmag.2016.080.055. S2CID   132760382.
  10. Vagn Buchwald (1975). Handbook of Iron Meteorites. Univ of California. ISBN   0-520-02934-8.
  11. Julian E. Andrews (2004). An introduction to environmental chemistry. Wiley-Blackwell. p. 269. ISBN   0-632-05905-2.
  12. Kurt Konhauser (2007). Introduction to geomicrobiology. Wiley-Blackwell. p. 320. ISBN   978-0-632-05454-1.
  13. Haloda, Jakub; Týcová, Patricie; Korotev, Randy L.; Fernandes, Vera A.; Burgess, Ray; Thöni, Martin; Jelenc, Monika; Jakeš, Petr; et al. (2009). "Petrology, geochemistry, and age of low-Ti mare-basalt meteorite Northeast Africa 003-A: A possible member of the Apollo 15 mare basaltic suite". Geochimica et Cosmochimica Acta. 73 (11): 3450. Bibcode:2009GeCoA..73.3450H. doi:10.1016/j.gca.2009.03.003.
  14. Grant Heiken; David Vaniman; Bevan M. French (1991). Lunar sourcebook. CUP Archive. p.  150. ISBN   0-521-33444-6.
  15. L. A. Tayrol; Williams, K. L. (1973). "Cu-Fe-S Phases in Lunar Rocks" (PDF). American Mineralogist. 58: 952. Bibcode:1973AmMin..58..952T.
  16. Yanai, Keizo (1997). "General view of twelve martian meteorites". Mineralogical Journal. 19 (2): 65–74. Bibcode:1997MinJ...19...65Y. doi: 10.2465/minerj.19.65 .
  17. Yu, Y; Gee, J (2005). "Spinel in Martian meteorite SaU 008: implications for Martian magnetism" (PDF). Earth and Planetary Science Letters. 232 (3–4): 287. Bibcode:2005E&PSL.232..287Y. doi:10.1016/j.epsl.2004.12.015. Archived from the original (PDF) on 2006-10-04.
  18. "Troilite". Mindat.org . Retrieved 2009-07-07.
  19. Fran Bagenal; Timothy E. Dowling; William B. McKinnon (2007). Jupiter. Cambridge University Press. p. 286. ISBN   978-0-521-03545-3.