Changbaiite

Changbaiite
Changbaiite
General
Category Oxide minerals
Chemical formula PbNb2O6
Strunz classification 04.DF.10
Identification
Molar mass 489.01 gram/mole
Color Colorless, Cream white, Pale brown, Yellow brown, Pale yellow green
Crystal habit Tabular - Form dimensions are thin in one direction.
Crystal system Trigonal - Ditrigonal PyramidalH-M Symbol (3m) Space Group: R 3
Cleavage {0001} Perfect, {1011} Distinct
Mohs scale hardness 5.5
Luster Adamantine - Pearly
Streak white
Diaphaneity Transparent
Optical properties Uniaxial (+), w=2.476, e=2.485, bire=0.0090.
References [1][2][3]

Changbaiite (PbNb2O6) is a member of the oxide mineral class in which the mineral contains oxygen grouped with one or two metal ion. Changbaiite is classified as a multiple Oxide XY2O6 and it generally have ionic bond.[4] Furthermore, it is also orthorhombic at a temperature of 25 degrees and it changes to orthorhombic-tetragonal at 570 degrees.[5]

Contents

Composition

The chemical formula of changbaiite is PbNb2O6 after microprobe analysis of kaolinite-filled veins. It is composed of iron (II) oxide FeO 0.94%, lead oxide PbO 41.51%, iron (III) oxide Fe2O3 0.42%, titanium dioxide TiO2 0.95%, niobium pentoxide Nb2O5 55.62%, and tantalum pentoxide Ta2O5 0.98%, which produce the chemical formula (Pb0.95Fe2+0.05)(Nb1.95Ti0.05Fe3+0.02Ta0.01) or PbNb2O6. It was also examined by the spectrographic method which represents Sb 0.3, Si 0.1, Ba 0.2, Ca 0.1, and minor traces of copper, magnesium and aluminum.[6]

Subbarao suggested that Changbaiite formula PbNb2O6 can vary. He represented lead niobate by A1+xNb2O6 where the A site is an ion (usually lead) and he found that the upper limit of x in his representation was about 0.15 and a low limit between -0.07 and -0.08.in conclusion, the formula ranges from Pb0.92Nb2O6 to Pb1.15Nb2O6.[5]

Geological occurrence

Changbaiite can be found in kaolinite cavities and potassic granite[3], which can be found in Tonghua, Southeastern Kirin, China.[6] Changbaiite was named after Changbai Mountain in China because it was found there.

Atomic structure

According to Subbarao[5] changbaiite is orthorhombic at 25°C with unit cell dimensions of a=17.65, b=17.91, c=7.736 angstrom and because its big unit cell size it's difficult to do a full structure analysis of PbNb2O6.[5] Changbaiite structure is composed of NbO6 octahedral crystals connected at their corners forming circles of 3 to 5 octahedral.[5] The NbO6 "cage" has coordination of 8 around oxygen. and the "tunnels" have a coordination of 10 around the Pb2+.[5]

Physical properties

Changbaiite has a trigonal crystal system and a space group of R3m. Its lattice dimensions are a= 10.499A c = 11.553A.[6] Changbaiite can be found as a small crystal with a tabular or spherules crystal shape. It can get up to 5mm in size and averages from 0.2 to 0.4mm.[6] Changbaiite’s trigonal crystals show 3m symmetry and is bounded, in sequence of lessening prominence. Normally it is colorless or sometimes appears in different schemes of colors like cream white, pale brown, yellowish-brown, pale yellowish-green with white streaks and adamantine to pearly luster.[6]

Changbaiite is nonmagnetic and breakable. Also, it possesses dual quality of translucent to transparent. It has perfect basal cleavage and distinct rhombohedral cleavage with hackly fracture, on the other side spherulitic grains are conchoidal.[6] Ultraviolet light and cathode rays have no fluorescent effect on changbaiite and this is not soluble in hydrochloric acid, nitric acid or sulphuric acid but conditionally less soluble in hot phosphoric acid.[6]. Changbaiite has a hardness of 472.4 kg/mm2 on the Vickers hardness scale and 5.3 on mohs scale.[6] In a optical spectrum changbaiite is uniaxial positive and it can be biaxial. Changbaiite reflectance, which is the fraction of incident radiation reflected by a surface, is 15.86 at 546 nm.[6]

Special characteristics

Changbaiite is considered to be a ferroelectric mineral. Ferroelectric minerals helped in the development of high-dielectric-constant capacitors and the development of piezoelectric transducers. In the medical field, ferroelectric minerals helped in developing the ultrasonic composite. Ferroelectric minerals are the main cause of many successful industries with high revenues.[7]

References

  1. ^ http://webmineral.com/data/Changbaiite.shtml Webmineral
  2. ^ http://www.mindat.org/min-968.html Mindat
  3. ^ a b Anthony, J.W., Bideaux, R., Bladh, K. and Nichols, M. (2003) Changbaiite PbNb2O6.Handbook of Mineralogy.Mineral Data Publishing Changbaiite
  4. ^ Klein, Cornelis; and Barbara Dutrow (2007). The 23rd edition of the manual of mineral science. New York: John Wiley & Sons. pp. 836 pp. ISBN 0-471-72157-3. 
  5. ^ a b c d e f Subbarao, E.C., and Shirane, G.(1960) Nonstoichiometry and Ferroelectric Properties of PbNb2O6-Type Compounds. JOURNAL OF CHEMICAL PHYSICS, 32, 1846-1851. Ferroelectric Properties of PbNb2O6-Type Compounds
  6. ^ a b c d e f g h i Fleischer, M., Chao, G.,and Pabst, A.(1979) New mineral names. American Mineralogist,64, 241-245.New Mineral Names
  7. ^ Haertling, G.H.(1999) Ferroelectric ceramics: history and technology, Journal of the American ceramic.82.797-818

Wikimedia Foundation. 2010.

Игры ⚽ Поможем решить контрольную работу

Look at other dictionaries:

  • List of minerals C-E (complete) — It is currently not possible to have a complete list of minerals . The International Mineralogical Association is the international group that recognises new minerals and new mineral names, however minerals discovered before 1959 did not go… …   Wikipedia

  • Liste des mineraux (lettre C) — Liste des minéraux (lettre C) liste des minéraux A B C D E F G H I J K L M N O P Q R S T U V W …   Wikipédia en Français

  • Liste des minéraux (lettre C) — v · Liste des minéraux A • B • C • D • E • F  …   Wikipédia en Français

  • Liste des minéraux (lettre c) — liste des minéraux A B C D E F G H I J K L M N O P Q R S T U V W …   Wikipédia en Français

  • Minéraux composites (lettre C) — Liste des minéraux (lettre C) liste des minéraux A B C D E F G H I J K L M N O P Q R S T U V W …   Wikipédia en Français

  • Oxide minerals — Oxide mineral exhibit at the Museum of Geology in South Dakota The oxide mineral class includes those minerals in which the oxide anion (O2 ) is bonded to one or more metal ions. The hydroxide bearing minerals are typically included in the oxide… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”