Perovskite

(mineralogy) Ca[TiO₃] A natural, yellow, brownish-yellow, reddish, brown, or black mineral and a structure type which includes no less than 150 synthetic compounds; the crystal structure is ideally cubic, it occurs as rounded cubes modified by the octahedral and dodecahedral forms, luster is subadamantine to submetallic, hardness is 5.5 on Mohs scale, and specific gravity is 4.0.

A minor accessory mineral, formula CaTiO₃, occurring in basic rocks. Perovskite has given its name to a large family of materials, synthetic and natural, crystallizing in similar structures. The crystal structure is ideally cubic, with a framework of corner-sharing octahedra, containing titanium (Ti) or other relatively small cations surrounded by six oxygen (O) or fluorine (F) anions. Within this framework are placed calcium (Ca) or other large cations, surrounded by twelve anions. Tilting of the octahedra and other distortions often lower the symmetry from cubic, giving the materials important ferroelectric properties and decreasing the coordination of the central cation. This flexibility gives the structure the ability to incorporate ions of different sizes and charges. Substitution of niobium (Nb), cerium (Ce), and other rare-earth elements in natural calcium titanate (CaTiO₃) is common and can make perovskite an ore for these elements. See also Coordination chemistry; Crystal structure; Rare-earth elements.

A number of synthetic perovskites are of major technological importance. Barium titanate (BaTiO₃) and lead zirconate-titanate (PZT) ceramics form the basis of a sizable industry in ferroelectric and piezoelectric materials crucial to transducers, capacitors, and electronics. Lanthanum chromate (LaCrO₃) and related materials find applications in fuel cells and high-temperature electric heaters. See also Ceramics; Fuel cell; Solid-state chemistry.

This article is about the mineral, for the crystal structure see perovskite structure

Perovskite
General
Category	Oxide mineral
Chemical formula	CaTiO3
Identification
Molar mass	135.96
Color	Black, Reddish brown, Pale yellow, Yellowish orange
Crystal habit	Pseudo cubic - crystals show a cubic outline
Crystal system	Orthorhombic (2/m 2/m 2/m) Space Group: P nma
Twinning	complex penetration twins
Cleavage	[100] good, [010] good, [001] good
Fracture	Conchoidal
Mohs Scale hardness	5 - 5.5
Luster	Adamantine to metallic; may be dull
Streak	grayish white
Diaphaneity	Transparent to opaque
Specific gravity	3.98–4.26
Optical properties	Biaxial (+)
Refractive index	a=2.3, b=2.34, g=2.38
Other characteristics	non-radioactive, non-magnetic
References	[1][2]

Perovskite, is a calcium titanium oxide mineral species composed of calcium titanate, with the chemical formula CaTiO₃.

The mineral was discovered in the Ural mountains of Russia by Gustav Rose in 1839 and is named after Russian mineralogist, L. A. Perovski (1792-1856).^[1]

It lends its name to the class of compounds which have the same type of crystal structure as CaTiO₃, known as the perovskite structure.

Occurrence

Perovskite is found in contact carbonate skarns at Magnet Cove, Arkansas. It occurs in altered blocks of limestone ejected from Mount Vesuvius. It occurs in chlorite and talc schist in the Urals and Switzerland.^[3] It is also found as an accessory mineral in alkaline and mafic igneous rocks, nepheline syenite, melilitite, kimberlites and rare carbonatites. Perovskite is a common mineral in the Ca-Al-rich inclusions found in some chondritic meteorites.^[2]

A rare earth bearing variety, knopite, (Ca,Ce,Na)(Ti,Fe)O₃) is found in alkali intrusive rocks in the Kola Peninsula and near Alnö, Sweden. A niobium bearing variety, dysanalyte, occurs in contact metamorphosed limestone in Baden, Germany.^[4][5][6][3]

References

1. ^ ^{a b} http://webmineral.com/data/Perovskite.shtml Webmineral data
2. ^ ^{a b} http://rruff.geo.arizona.edu/doclib/hom/perovskite.pdf Handbook of Mineralogy
3. ^ ^{a b} Palache, Charles, Harry Berman and Clifford Frondel, 1944, Dana's System of Mineralogy Vol. 1, Wiley, 7th ed. p. 733
4. ^ Deer, Howie and Zussman, An Introduction to the Rock Forming Minerals Longman 1966, ISBN 0582442109
5. ^ http://www.mindat.org/min-2228.html Mindat - knopite
6. ^ http://www.mindat.org/min-11023.html Mindat - dysanalyte

See also

• Calcium titanate
• Perovskite (structure)
• Post-perovskite

v • d • e Titanium minerals Oxides Simple Anatase · Brookite · Rutile Mixed Aeschynite-(Y) · Armalcolite · Betafite · Euxenite · Haggertyite · Hibonite · Ilmenite · Keilhauite · Perovskite · Polycrase · Zirconolite · Zirkelite Silicates Aenigmatite · Keilhauite · Lorenzenite · Melanite · Nenadkevichite · Titanite · Zircophyllite Other Heavy mineral sands (various) · Sabinaite (carbonate) · Warwickite (borate) · Zimbabweite (arsenite)

This article about a specific oxide mineral is a stub. You can help Wikipedia by expanding it.

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)