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, silica (silicon dioxide, ) is usually consid ...
. It is mostly composed of
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) 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, right in f ...
,
silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...
and
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
, with smaller fractions of
calcium
Calcium is a chemical element with the 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 ...
and several other metals.
[ Together with armalcolite and ]tranquillityite
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 Tranqui ...
, it is one of the three minerals which were discovered on the Moon. It was then found in Lunar
Lunar most commonly means "of or relating to the Moon".
Lunar may also refer to:
Arts and entertainment
* ''Lunar'' (series), a series of video games
* "Lunar" (song), by David Guetta
* "Lunar", a song by Priestess from the 2009 album ''Prior t ...
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 percen ...
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
Pyroxmangite has the general chemical formula of MnSiO3. It is the high-pressure, low-temperature dimorph of rhodonite.
It was first described in 1913 and named for the mineral group, pyroxenes, and is known as the manganese member. It forms a ...
.[ 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 a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of ...
; 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 as ...
samples from the Sea of Tranquility during the Apollo
Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label=Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label= ...
missions.[ Together with armalcolite and ]tranquillityite
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 Tranqui ...
, 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 percen ...
s recovered in Oman
Oman ( ; ar, عُمَان ' ), officially the Sultanate of Oman ( ar, سلْطنةُ عُمان ), is an Arabian country located in southwestern Asia. It is situated on the southeastern coast of the Arabian Peninsula, and spans the mouth of t ...
. It also occurs in the Earth's crust, in association with clinopyroxene
The pyroxenes (commonly abbreviated to ''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 calcium (Ca), sodium (Na), iron (Fe II) ...
, plagioclase
Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more prope ...
, 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, printing ...
, cristobalite
Cristobalite is a mineral polymorph of silica that is formed at very high temperatures. It has the same chemical formula as quartz, SiO2, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members of the ...
, tridymite
Tridymite is a high-temperature 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 Si O2. Tridymite was first described ...
, fayalite
Fayalite (, commonly abbreviated to Fa) is the iron-rich end-member of the olivine solid-solution series. In common with all minerals in the olivine group, fayalite crystallizes in the orthorhombic system (space group ''Pbnm'') with cell para ...
, 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, bl ...
and potassic feldspar
Feldspars are 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 ''plagioclase'' (sodium-calcium) feldsp ...
, and forms series with pyroxmangite
Pyroxmangite has the general chemical formula of MnSiO3. It is the high-pressure, low-temperature dimorph of rhodonite.
It was first described in 1913 and named for the mineral group, pyroxenes, and is known as the manganese member. It forms a ...
. Pyroxferroite has been found in the Isanago mine
Mine, mines, miners or mining may refer to:
Extraction or digging
* Miner, a person engaged in mining or digging
*Mining, extraction of mineral resources from the ground through a mine
Grammar
*Mine, a first-person English possessive pronoun
...
, in Kyoto Prefecture, Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
; near Iva, Anderson County, South Carolina, USA; from Väster Silfberg, Värmland
Värmland () also known as Wermeland, is a '' landskap'' (historical province) in west-central Sweden. It borders Västergötland, Dalsland, Dalarna, Västmanland, and Närke, and is bounded by Norway in the west. Latin name versions are ''Va ...
, Sweden
Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...
; and Lapua
Lapua (; sv, Lappo) is a town and municipality of Finland.
It is located next to the Lapua River in the region of South Ostrobothnia. The town has a population of
() and covers an area of of
which is water. The population density is . The mun ...
, Finland
Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of B ...
.[ 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 whic ...
which is rare on Earth, but is common on the Moon and Mars.[
]
Synthesis
Synthetic pyroxferroite crystals can be produced by compressing synthetic clinopyroxene
The pyroxenes (commonly abbreviated to ''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 calcium (Ca), sodium (Na), iron (Fe II) ...
(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 with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...
, pyroxene
The pyroxenes (commonly abbreviated to ''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 calcium (Ca), sodium (Na), iron (Fe II) ...
and a silicon dioxide
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...
phase, whereas at low temperatures, it transforms to a clinopyroxene.[ The presence of ]cristobalite
Cristobalite is a mineral polymorph of silica that is formed at very high temperatures. It has the same chemical formula as quartz, SiO2, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members of the ...
, 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 of ...
and some other petrographic
Petrography is a branch of petrology that focuses on detailed descriptions of rocks. Someone who studies petrography is called a petrographer. The mineral content and the textural relationships within the rock are described in detail. The class ...
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.
![PyroxferroiteStructure](https://upload.wikimedia.org/wikipedia/commons/0/02/PyroxferroiteStructure.png)
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