Troilite
Encyclopedia
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.
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
. 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.
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. For this reason, troilite is sometimes called pyrrhotite-2C.
, 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. In 1862 German mineralogist Gustav Rose
analyzed the material and recognized it as stoichiometric FeS and gave it the name troilite in recognition of the work of Domenico Troili.
, sphalerite
, graphite
, and a variety of phosphate
and silicate minerals
. 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
, and at Nordfjellmark, Norway
. In the Australian occurrence it is associated with copper, nickel iron ore deposits occurring with pyrrhotite, pentlandite
, mackinawite
, cubanite
, valleriite, chalcopyrite
and pyrite.
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. 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. 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, bacteria reduce 1.07 times faster than that may increase the / ratio by up to 10%.
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.
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%.
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
. 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.
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
sulfide mineral
Sulfide mineral
The sulfide minerals are a class of minerals containing sulfide as the major anion. Some sulfide minerals are economically important as metal ores. The sulfide class also includes the selenides, the tellurides, the arsenides, the antimonides, the bismuthinides, the sulfarsenides and the sulfosalts...
with the simple formula of FeS. It is the iron rich endmember of the pyrrhotite
Pyrrhotite
Pyrrhotite is an unusual iron sulfide mineral with a variable iron content: FeS . The FeS endmember is known as troilite. Pyrrhotite is also called magnetic pyrite because the color is similar to pyrite and it is weakly magnetic...
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.
Troilite can be found as a native mineral on Earth, but is more abundant in meteorites, in particular those originating from the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
and Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
. Uniform presence of troilite on the Moon and possibly on Mars has been confirmed by the Apollo, Viking
Viking program
The Viking program consisted of a pair of American space probes sent to Mars, Viking 1 and Viking 2. Each spacecraft was composed of two main parts, an orbiter designed to photograph the surface of Mars from orbit, and a lander designed to study the planet from the surface...
and Phobos
Phobos program
The Phobos program was an unmanned space mission consisting of two probes launched by the Soviet Union to study Mars and its moons Phobos and Deimos. Phobos 2 became a Mars orbiter and returned 38 images with a resolution of up to 40 meters...
space probes. The relative intensities of isotopes of sulfur
Isotopes of sulfur
Sulfur has 25 known isotopes with mass numbers ranging from 26 to 49, four of which are stable: 32S , 33S , 34S , and 36S...
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.
Structure
Troilite has hexagonal structure (Pearson symbolPearson symbol
The Pearson symbol, or Pearson notation, is used in crystallography as a means of describing a crystal structure, and was originated by W.B. Pearson. The symbol is made up of two letters followed by a number. For example:* Diamond structure, cF8...
hP24, Space group
Space group
In mathematics and geometry, a space group is a symmetry group, usually for three dimensions, that divides space into discrete repeatable domains.In three dimensions, there are 219 unique types, or counted as 230 if chiral copies are considered distinct...
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. For this reason, troilite is sometimes called pyrrhotite-2C.
Discovery
A meteorite fall was observed in 1766 at AlbaretoAlbareto
Albareto is a comune in the Province of Parma in the Italian region Emilia-Romagna, located about 130 km west of Bologna and about 60 km southwest of Parma....
, Modena
Modena
Modena is a city and comune on the south side of the Po Valley, in the Province of Modena in the Emilia-Romagna region of Italy....
, Italy. Samples were collected and studied by Domenico Troili
Domenico Troili
Domenico Troili was an Italian abbate and a Jesuit, who held the appointment of custodian of the library of the ruling family of Este in Modena...
who described the iron sulfide inclusions in the meteorite. These iron sulfides were long considered to be pyrite. In 1862 German mineralogist Gustav Rose
Gustav Rose
Gustav Rose was a German mineralogist who was a native of Berlin. He was a brother of mineralogist Heinrich Rose , the son of pharmacologist Valentin Rose , and the father of noted surgeon Edmund Rose and the classicist Valentin Rose.He was a graduate of the University of Berlin, where he was a...
analyzed the material and recognized it as stoichiometric FeS and gave it the name troilite in recognition of the work of Domenico Troili.
Occurrence
Troilite has been reported from a variety of meteorites occurring with daubreelite, chromiteChromite
Chromite is an iron chromium oxide: FeCr2O4. It is an oxide mineral belonging to the spinel group. Magnesium can substitute for iron in variable amounts as it forms a solid solution with magnesiochromite ; substitution of aluminium occurs leading to hercynite .-Occurrence:Chromite is found in...
, sphalerite
Sphalerite
Sphalerite is a mineral that is the chief ore of zinc. It consists largely of zinc sulfide in crystalline form but almost always contains variable iron. When iron content is high it is an opaque black variety, marmatite. It is usually found in association with galena, pyrite, and other sulfides...
, graphite
Graphite
The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...
, and a variety of phosphate
Phosphate minerals
Phosphate minerals are those minerals that contain the tetrahedrally coordinated phosphate anion along with the freely substituting arsenate and vanadate...
and silicate minerals
Silicate minerals
The silicate minerals make up the largest and most important class of rock-forming minerals, constituting approximately 90 percent of the crust of the Earth. They are classified based on the structure of their silicate group...
. It has also been reported from serpentinite
Serpentinite
Serpentinite is a rock composed of one or more serpentine group minerals. Minerals in this group are formed by serpentinization, a hydration and metamorphic transformation of ultramafic rock from the Earth's mantle...
in the Alta mine, Del Norte County, California
Del Norte County, California
Del Norte County is a county located at the far northwest corner of the U.S. state of California on the Pacific adjacent to the Oregon border. As of the 2010 census, it had a population of 28,610. The county seat is Crescent City, the county's only incorporated city. Del Norte is the abbreviated...
and in layered igneous intrusions in Western Australia, the Ilimaussaq intrusion
Ilimaussaq intrusive complex
The Ilimaussaq intrusive complex is a large alkalic layered intrusion located on the southwest coast of Greenland. It is Mesoproterozoic in age. It is the type locality of agpaitic nepheline syenite and hosts a variety of unusual rock types....
of southern Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
, and at Nordfjellmark, Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
. In the Australian occurrence it is associated with copper, nickel iron ore deposits occurring with pyrrhotite, pentlandite
Pentlandite
Pentlandite is an iron-nickel sulfide, 9S8. Pentlandite usually has a Ni:Fe ratio of close to 1:1. It also contains minor cobalt.Pentlandite forms isometric crystals, but is normally found in massive granular aggregates. It is brittle with a hardness of 3.5 - 4 and specific gravity of 4.6 - 5.0 and...
, mackinawite
Mackinawite
Mackinawite is an iron nickel sulfide mineral with formula 1 + xS . It crystallizes in the tetragonal crystal system and 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.-Occurrence:It occurs in serpentinized...
, cubanite
Cubanite
Cubanite is a yellow mineral of copper, iron, and sulfur, CuFe2S3.Cubanite was first described in 1843 for an occurrence in the Mayarí-Baracoa Belt, Oriente Province, Cuba....
, valleriite, chalcopyrite
Chalcopyrite
Chalcopyrite is a copper iron sulfide mineral that crystallizes in the tetragonal system. It has the chemical composition CuFeS2. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green tinged black.On exposure to air, chalcopyrite...
and pyrite.
Troilite is extremely rarely encountered in the Earth's crust. (Even pyrrhotite is relatively rare compared to pyrite and Iron(II) sulfate
Iron(II) sulfate
Iron sulfate or ferrous sulfate is the chemical compound with the formula FeSO4. Known since ancient times as copperas and as green vitriol, the blue-green heptahydrate is the most common form of this material...
minerals) Most troilite on Earth is of meteoritic origin. One iron meteorite, Mundrabilla contains 25 to 35 volume percent troilite. 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. 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, bacteria reduce 1.07 times faster than that may increase the / ratio by up to 10%.
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
Apollo 11
In early 1969, Bill Anders accepted a job with the National Space Council effective in August 1969 and announced his retirement as an astronaut. At that point Ken Mattingly was moved from the support crew into parallel training with Anders as backup Command Module Pilot in case Apollo 11 was...
, 12
Apollo 12
Apollo 12 was the sixth manned flight in the American Apollo program and the second to land on the Moon . It was launched on November 14, 1969 from the Kennedy Space Center, Florida, four months after Apollo 11. Mission commander Charles "Pete" Conrad and Lunar Module Pilot Alan L...
, 15
Apollo 15
Apollo 15 was the ninth manned mission in the American Apollo space program, the fourth to land on the Moon and the eighth successful manned mission. It was the first of what were termed "J missions", long duration stays on the Moon with a greater focus on science than had been possible on previous...
and 16
Apollo 16
Young and Duke served as the backup crew for Apollo 13; Mattingly was slated to be the Apollo 13 command module pilot until being pulled from the mission due to his exposure to rubella through Duke.-Backup crew:...
missions contain about 1% of troilite.
Troilite is regularly found in Martian meteorites (i.e. those originating from Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
). Similar to the Moon's surface and meteorites, the fraction of troilite in Martian meteorites is close to 1%.
Based on observations by the Voyager
Voyager program
The Voyager program is a U.S program that launched two unmanned space missions, scientific probes Voyager 1 and Voyager 2. They were launched in 1977 to take advantage of a favorable planetary alignment of the late 1970s...
spacecraft in 1979 and Galileo in 1996, troilite might also be present in the rocks of Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
’s satellites Ganymede
Ganymede (moon)
Ganymede is a satellite of Jupiter and the largest moon in the Solar System. It is the seventh moon and third Galilean satellite outward from Jupiter. Completing an orbit in roughly seven days, Ganymede participates in a 1:2:4 orbital resonance with the moons Europa and Io, respectively...
and Callisto
Callisto (moon)
Callisto named after the Greek mythological figure of Callisto) is a moon of the planet Jupiter. It was discovered in 1610 by Galileo Galilei. It is the third-largest moon in the Solar System and the second largest in the Jovian system, after Ganymede. Callisto has about 99% the diameter of the...
. 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.