Pyroxferroite (Fe
2+,Ca)SiO
3 is a single chain
inosilicate
Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust.
In mineralogy, the crystalline forms of silica (silicon dio ...
. It is mostly composed of
iron
Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
,
silicon
Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...
and
oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
, with smaller fractions of
calcium
Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...
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
Apollo 11 was a spaceflight conducted from July 16 to 24, 1969, by the United States and launched by NASA. It marked the first time that humans Moon landing, landed on the Moon. Commander Neil Armstrong and Lunar Module pilot Buzz Aldrin l ...
mission. It was then found in Lunar and Martian meteorite
A Martian meteorite is a rock that formed on Mars, was ejected from the planet by an impact event, and traversed interplanetary space before landing on Earth as a meteorite. , 277 meteorites had been classified as Martian, less than half a perce ...
s 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.
Etymology
Pyroxferroite is named from ''pyroxene'' and ''ferrum'' (Latin for iron), as the iron-rich analogue of pyroxmangite.[ The word pyroxene, in turn comes from the Greek words for ''fire'' (πυρ) and ''stranger'' (ξένος). Pyroxenes were named this way because of their presence in volcanic lavas, where they are sometimes seen as crystals embedded in volcanic ]glass
Glass is an amorphous (non-crystalline solid, non-crystalline) solid. Because it is often transparency and translucency, transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window pane ...
; it was assumed they were impurities in the glass, hence the name "fire strangers". However, they are simply early-forming minerals that crystallized before the lava erupted.
Occurrence
Pyroxferroite was first discovered in 1969 in lunar rock
Moon rock or lunar rock is rock originating from Earth's Moon. This includes lunar material collected during the course of human exploration of the Moon, and rock that has been ejected naturally from the Moon's surface and landed on Earth a ...
samples from Tranquility Base
Tranquility Base () is the site on the Moon where, in July 1969, humans landed and walked on a celestial body other than Earth for the first time. On July 20, 1969, Apollo 11 crewmembers Neil Armstrong and Buzz Aldrin landed their Apollo Lunar Mo ...
, the Sea of Tranquility
Mare Tranquillitatis (Latin for Sea of Tranquillity or Sea of Tranquility) is a lunar mare that sits within the Tranquillitatis basin on the Moon. It contains Tranquility Base, the first location on another celestial body to be visited by hu ...
landing site of Apollo
Apollo is one of the Twelve Olympians, Olympian deities in Ancient Greek religion, ancient Greek and Ancient Roman religion, Roman religion and Greek mythology, Greek and Roman mythology. Apollo has been recognized as a god of archery, mu ...
11.[ Together with armalcolite and tranquillityite, it is one of the three minerals which were first found on the Moon. Later, pyroxferroite was detected in Lunar and ]Martian meteorite
A Martian meteorite is a rock that formed on Mars, was ejected from the planet by an impact event, and traversed interplanetary space before landing on Earth as a meteorite. , 277 meteorites had been classified as Martian, less than half a perce ...
s recovered in Oman
Oman, officially the Sultanate of Oman, is a country located on the southeastern coast of the Arabian Peninsula in West Asia and the Middle East. It shares land borders with Saudi Arabia, the United Arab Emirates, and Yemen. Oman’s coastline ...
. It also occurs in the Earth's crust, in association with clinopyroxene
The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron (Fe ...
, plagioclase
Plagioclase ( ) is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continu ...
, ilmenite
Ilmenite is a titanium-iron oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used in paints, printi ...
, cristobalite
Cristobalite ( ) is a mineral polymorph of silica that is formed at very high temperatures. It has the same chemical formula as quartz, Si O2, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members o ...
, tridymite
Tridymite is a high-temperature polymorphism (materials science), polymorph of silica and usually occurs as minute tabular white or colorless pseudo-hexagonal crystals, or scales, in cavities in felsic volcanic rocks. Its chemical formula is sili ...
, fayalite
Fayalite (, commonly abbreviated to Fa) is the iron-rich endmember, end-member of the olivine solid solution, solid-solution series. In common with all minerals in the olivine, olivine group, fayalite crystallizes in the orthorhombic system (spac ...
, fluorapatite
Fluorapatite, often with the alternate spelling of fluoroapatite, is a phosphate mineral with the formula Ca5(PO4)3F (calcium fluorophosphate). Fluorapatite is a hard crystalline solid. Although samples can have various color (green, brown, blu ...
and potassic feldspar
Feldspar ( ; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagiocl ...
, and forms series with pyroxmangite. Pyroxferroite has been found in the Isanago mine, in Kyoto Prefecture
is a Prefectures of Japan, prefecture of Japan located in the Kansai region of Honshu. Kyoto Prefecture has a population of 2,561,358 () and has a geographic area of . Kyoto Prefecture borders Fukui Prefecture to the northeast, Shiga Prefecture ...
, Japan
Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
; near Iva, Anderson County, South Carolina
Anderson County is a county located in the U.S. state of South Carolina. As of the 2020 census, its population was 203,718. Its county seat is Anderson. Named for Revolutionary War leader Robert Anderson, the county is located in northwest ...
, US; from Väster Silfberg, Värmland
Värmland () is a ''Provinces of Sweden, landskap'' (historical province) in west-central Sweden. It borders Västergötland, Dalsland, Dalarna, Västmanland, and Närke, and is bounded by Norway in the west.
Name
Several Latinized version ...
, Sweden
Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...
; and Lapua
Lapua (; ) is a List of cities and towns in Finland, town and municipalities of Finland, municipality in Finland's South Ostrobothnia regions of Finland, region.
It is located next to the Lapua River. The town has a population of
() and cov ...
, Finland
Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...
.[ In the original lunar samples, pyroxferroite was associated with similar minerals, but also with ]troilite
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 is rare on Earth, but is common on the Moon and Mars.[
]
Synthesis
Synthetic pyroxferroite crystals can be produced by compressing synthetic clinopyroxene (composition Ca0.15Fe0.85SiO3) to a pressure in the range of 10–17.5 kbar and heating it to 1130–1250 °C. It is metastable at low temperatures and pressures: at pressures below 10 kbar pyroxferroite converts to a mixture of olivine
The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...
, pyroxene
The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron ( ...
and a silicon dioxide
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundan ...
phase, whereas at low temperatures, it transforms to a clinopyroxene.[ The presence of cristobalite, ]vesicular texture
Vesicular texture is a volcanic rock texture characterized by a rock being pitted with many cavities (known as vesicles) at its surface and inside.
This texture is common in aphanitic, or glassy, igneous rocks that have come to the surface ...
and some other petrographic observations indicate that the lunar pyroxferroite was produced upon rapid cooling from low-pressure and high-temperature (volcanic) conditions, i.e. that the mineral is metastable. However, the conversion rate is very slow and pyroxferroite can exist at low temperatures for periods longer than 3 billion years.
Properties
The crystal structure of pyroxferroite contains silicon-oxygen chains with a repeat period of seven SiO4 tetrahedra. These chains are separated by polyhedra where a central metal atom is surrounded by 6 or 7 oxygen atoms; there are 7 inequivalent metal polyhedra in the unit cell. The resulted layers are parallel to (110) planes in pyroxferroite, whereas they are parallel to (100) planes in pyroxenes.
Chemical composition of pyroxferroite can be decomposed into elementary oxides as follows: FeO (concentration 44–48%), SiO2(45–47%), CaO (4.7–6.1%), MnO (0.6–1.3%), MgO (0.3-1%), TiO2 (0.2–0.5%) and Al2O3 (0.2–1.2%). Whereas magnesium is usually present at about 0.8%, in some samples it had an undetectably low concentration.[
]
References
{{Manganese minerals
Inosilicates
Iron(II) minerals
Manganese(II) minerals
Calcium minerals
Pyroxene group
Triclinic minerals
Minerals in space group 2
Apollo 11
Minerals described in 1970