Perovskite

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This article is about the mineral, for the crystal structure see perovskite structure
Perovskite
General
CategoryOxide minerals
Formula
(repeating unit)		CaTiO3
Strunz classification04.CC.30
Crystal systemOrthorhombic (2/m 2/m 2/m) space group: Pnma
Identification
Formula mass135.96
ColorBlack, reddish brown, pale yellow, yellowish orange
Crystal habitPseudo cubic – crystals show a cubic outline
Twinningcomplex penetration twins
Cleavage[100] good, [010] good, [001] good
FractureConchoidal
Mohs scale hardness5–5.5
LusterAdamantine to metallic; may be dull
Streakgrayish white
DiaphaneityTransparent to opaque
Specific gravity3.98–4.26
Optical propertiesBiaxial (+)
Refractive indexnα=2.3, nβ=2.34, nγ=2.38
Other characteristicsnon-radioactive, non-magnetic
References[1][2][3][4][5][6][7][8]

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 Lev Perovski (1792–1856).[1]

It lends its name to the class of compounds which have the same type of crystal structure as CaTiO3 (XIIA2+VIIB4+X2–3) known as the perovskite structure.[9] The perovskite crystal structure was published in 1945 from X-ray diffraction data on barium titanate by the Irish crystallographer Helen Dick Megaw (1907–2002).[10]

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.[11] 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 carbonatite near Schelingen, Kaiserstuhl, Germany.[11][12][13][14]

Special characteristics

The stability of perovskite in igneous rocks is limited by its reaction relation with sphene. In volcanic rocks perovskite and sphene are not found together, the only exception being in an atindite from Cameroun.[4]

Physical properties

The sub-metallic to metallic luster, colorless streak, cube like structure along with imperfect cleavage and brittle tenacity are physical properties of perovskite. Colors range from black, brown, gray, orange to yellow. Crystals of perovskite appear as cubes, but are pseudocubic and crystallize in the orthorhombic system. Perovskite crystals have been mistaken for galena; however, galena has a better metallic luster, greater density, perfect cleavage and true cubic symmetry.[5]

Physical properties of interest to materials science among perovskites include superconductivity, magnetoresistance, ionic conductivity, and a multitude of dielectric properties, which are of great importance in microelectronics and telecommunication. Because of the flexibility of bond angles inherent in the perovskite structure there are many different types of distortions which can occur from the ideal structure. These include tilting of the octahedra, displacements of the cations out of the centers of their coordination polyhedra, and distortions of the octahedra driven by electronic factors (Jahn-Teller distortions).[6]

Geologic occurrence

Basically found in the earth’s mantle, the perovskite’s occurrence at Khibina Massif is restricted to the under saturated ultramafic rocks and foidolites, due to the instability in a paragenesis with feldspar. The complexity is made by an extended series of rocks from early alkaline ultramafic members to late carbonatites that comprise alkaline and mafic igneous rocks such as nepheline syenite, melilitite, kimberlite and rare carbonatites in ultramafites. Perovskite occurs as small anhedral to subhedral crystals filling interstices between the rock-forming silicates.[7]

Discovery and name

Perovskite was first described in 1839 from an occurrence in the Achmatovsk Mine in the Nazyamskie Mountains, Chelyabinsk Oblast, Southern Urals, Russia. The new mineral was named by Gustav Rose for Russian mineralogist, Count Lev Alekseevich Perovski (1792–1856), of St. Petersburg, Russia.[15][2]

See also

References

  1. ^ a b Perovskite. Webmineral
  2. ^ a b c John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, and Monte C. Nichols (Eds.) Perovskite. Handbook of Mineralogy. Mineralogical Society of America, Chantilly, VA
  3. ^ Naoki Inoue and Yanhui Zou Physical properties of perovskite-type lithium ionic conductor.Ch. 8 in Takashi Sakuma and Haruyuki Takahashi (Eds.) Physics of Solid State Ionics (2006) pp. 247–269 ISBN 81-308-0070-5
  4. ^ a b Veksler, I.V.; Teptelev, M.P. (1990). "Conditions for crystallization and concentration of perovskite-type minerals in alkaline magmas". Lithos. 26: 177. doi:10.1016/0024-4937(90)90047-5.
  5. ^ a b Luxová, Jana; Šulcová, Petra; Trojan, M. (2008). "Study of Perovskite" (PDF). Journal of Thermal Analysis and Calorimetry. 93 (3): 823. doi:10.1007/s10973-008-9329-z.
  6. ^ a b . doi:10.1107/S0108768103026661/pdf. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  7. ^ a b Anton R. Chakhmouradian and Roger H. Mitchell (1998). "Compositional variation of perovskite-group minerals from the Khibina Complex, Kola Peninsula, Russia" (PDF). The Canadian Mineralogist. 36: 953–969.
  8. ^ Lemanov, V (1999). "Perovskite CaTiO3 as an incipient ferroelectric". Solid State Communications. 110 (11): 611. doi:10.1016/S0038-1098(99)00153-2.
  9. ^ Wenk, Hans-Rudolf; Bulakh, Andrei (2004). Minerals: Their Constitution and Origin. New York, NY: Cambridge University Press. p. 413. ISBN 978-0-521-52958-7.
  10. ^ Megaw, Helen (1945). "Crystal Structure of Barium Titanate". Nature. 155 (3938): 484. doi:10.1038/155484b0.
  11. ^ a b Palache, Charles, Harry Berman and Clifford Frondel, 1944, Dana's System of Mineralogy Vol. 1, Wiley, 7th ed. p. 733
  12. ^ Deer, Howie and Zussman, An Introduction to the Rock Forming Minerals Longman 1966, ISBN 0-582-44210-9
  13. ^ Knopite. Mindat
  14. ^ Dysanalyte. Mindat
  15. ^ Perovskite. Mindat
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