Apatite


Apatite
Apatite
General
Category Phosphate mineral group
Chemical formula Ca5(PO4)3(F,Cl,OH)
Strunz classification 08.BN.05
Identification
Color Transparent to translucent, usually green, less often colorless, yellow, blue to violet, pink, brown.[1]
Crystal habit Tabular, prismatic crystals, massive, compact or granular
Crystal system Hexagonal dipyramidal (6/m)[2]
Cleavage [0001] indistinct, [1010] indistinct[2]
Fracture Conchoidal to uneven[1]
Mohs scale hardness 5[1] (defining mineral)
Luster Vitreous[1] to subresinous
Streak White
Diaphaneity Transparent to translucent[2]
Specific gravity 3.16–3.22[2]
Polish luster Vitreous[1]
Optical properties Double refractive, uniaxial negative[1]
Refractive index 1.634–1.638 (+0.012, −0.006)[1]
Birefringence 0.002–0.008[1]
Pleochroism Blue stones – strong, blue and yellow to colorless. Other colors are weak to very weak.[1]
Dispersion 0.013[1]
Ultraviolet fluorescence Yellow stones – purplish pink which is stronger in long wave; blue stones – blue to light blue in both long and short wave; green stones – greenish yellow which is stronger in long wave; violet stones – greenish yellow in long wave, light purple in short wave.[1]

Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH, F, Cl or Br ions, respectively, in the crystal. The formula of the admixture of the four most common endmembers is written as Ca10(PO4)6(OH,F,Cl,Br)2, and the crystal unit cell formulae of the individual minerals are written as Ca10(PO4)6(OH)2, Ca10(PO4)6(F)2, Ca10(PO4)6(Cl)2 and Ca10(PO4)6(Br)2.

Apatite is one of a few minerals that are produced and used by biological micro-environmental systems. Apatite is the defining mineral for 5 on the Mohs scale. Hydroxyapatite, also known as hydroxylapatite, is the major component of tooth enamel and bone mineral. A relatively rare form of apatite in which most of the OH groups are absent and containing many carbonate and acid phosphate substitutions is a large component of bone material.

Fluorapatite (or fluoroapatite) is more resistant to acid attack than is hydroxyapatite. For this reason, toothpaste typically contains a source of fluoride anions (e.g. sodium fluoride, sodium monofluorophosphate). Similarly, fluoridated water allows exchange in the teeth of fluoride ions for hydroxyl groups in apatite. Too much fluoride results in dental fluorosis and/or skeletal fluorosis.

Fission tracks in apatite are commonly used to determine the thermal history of orogenic (mountain) belts and of sediments in sedimentary basins. (U-Th)/He dating of apatite is also well established for use in determining thermal histories and other, less typical applications such as paleo-wildfire dating.

Phosphorite is a phosphate-rich sedimentary rock, that contains between 18% and 40% P2O5. The apatite in phosphorite is present as cryptocrystalline masses referred to as collophane.

Contents

Uses

Apatity, Russia, a site of apatite mines and processing facilities

The primary use of apatite is in the manufacture of fertilizer – it is a source of phosphorus. It is occasionally used as a gemstone.

During digestion of apatite with sulfuric acid to make phosphoric acid, hydrogen fluoride is produced as a byproduct from any fluorapatite content. This byproduct is a minor industrial source of hydrofluoric acid.[3]

Fluoro-chloro apatite forms the basis of the now obsolete Halophosphor fluorescent tube phosphor system. Dopant elements of manganese and antimony, at less than one mole-percent, in place of the calcium and phosphorus impart the fluorescence, and adjustment of the fluorine to chlorine ratio adjusts the shade of white produced. Now almost entirely replaced by the Tri-Phosphor system.[4]

In the United States, apatite derived fertilizers are used to supplement the nutrition of many agricultural crops by providing a valuable source of phosphate.

Gemology

Apatite is infrequently used as a gemstone. Transparent stones of clean color have been faceted, and chatoyant specimens have been cabochon cut.[1] Chatoyant stones are known as cat's-eye apatite,[1] transparent green stones are known as asparagus stone,[1] and blue stones have been called moroxite.[5] Crystals of rutile may have grown in the crystal of apatite so when in the right light, the cut stone displays a cat's eye effect. Major sources for gem apatite are[1] Brazil, Burma, and Mexico. Other sources include[1] Canada, Czechoslovakia, Germany, India, Madagascar, Mozambique, Norway, South Africa, Spain, Sri Lanka, and the United States.

Use as an ore mineral

Apatite is occasionally found to contain significant amounts of rare earth elements and can be used as an ore for those metals.[6] This is preferable to traditional rare earth ores, as apatite is non-radioactive [7] and does not pose an environmental hazard in mine tailings. Except some apatite in Florida used to produce phosphate for U.S. tobacco crops contains uranium, radium, lead 210 and polonium 210 and radon.[8][9]

Apatite is an ore mineral at the Hoidas Lake rare earth project.[10]

Thermodynamics

The standard (p = 0.1 MPa) molar enthalpies of formation in the crystalline state of hydroxyapatite, chlorapatite and a preliminary value for bromapatite, at T = 298.15 K, have already been determined by reaction-solution calorimetry. Speculations on the existence of a possible fifth member of the calcium apatites family, iodoapatite, have been drawn from energetic considerations.[11]

Lunar science

Moon rocks collected by astronauts during the Apollo program contain traces of apatite.[12] Re-analysis of these samples in 2010 revealed water trapped in the mineral as hydroxyl, leading to estimates of water on the lunar surface at a rate of at least 64 parts per billion – 100 times greater than previous estimates – and as high as 5 parts per million.[13] If the minimum amount of mineral-locked water was hypothetically converted to liquid, it would cover the Moon's surface in roughly one meter of water.[14]

See also

Apatite Crystal, Mexico

References

  1. ^ a b c d e f g h i j k l m n o p Gemological Institute of America, GIA Gem Reference Guide 1995, ISBN 0-87311-019-6
  2. ^ a b c d Apatite. Webmineral
  3. ^ Villalba, Gara; Ayres, Robert U.; Schroder, Hans (2008). "Accounting for Fluorine: Production, Use, and Loss". Journal of Industrial Ecology 11: 85–101. doi:10.1162/jiec.2007.1075. 
  4. ^ Henderson and Marsden, "Lamps and Lighting", Edward Arnold Ltd, 1972, ISBN 0-7131-3267-1
  5. ^ Streeter, Edwin W., Precious Stones and Gems 6th edition, George Bell and Sons, London, 1898, p306
  6. ^ Salvi S, Williams‐Jones A. 2004. Alkaline granite‐syenite deposits. In Linnen RL, Samson IM, editors. Rare element geochemistry and mineral deposits. St. Catharines (ON): Geological Association of Canada. pp. 315‐341 ISBN 1897095082
  7. ^ Haxel G, Hedrick J, Orris J. 2006. Rare earth elements critical resources for high technology. Reston (VA): United States Geological Survey. USGS Fact Sheet: 087‐02.
  8. ^ Proctor, Robert N. (2006-12-01) Puffing on Polonium – New York Times. Nytimes.com. Retrieved on 2011-07-24.
  9. ^ Tobacco Smoke | Radiation Protection | US EPA. Epa.gov (2006-06-28). Retrieved on 2011-07-24.
  10. ^ Great Western Minerals Group Ltd. | Projects – Hoidas Lake, Saskatchewan. Gwmg.ca (2010-01-27). Retrieved on 2011-07-24.
  11. ^ Cruz, F.J.A.L.; Minas da Piedade, M.E.; Calado, J.C.G. (2005). "Standard molar enthalpies of formation of hydroxy-, chlor-, and bromapatite". J. Chem. Thermodyn. 37 (10): 1061–1070. doi:10.1016/j.jct.2005.01.010. 
  12. ^ Smith, J. V., Anderson, A. T., Newton, R. C., Olsen, E. J., Crewe, A. V., Isaacson, M. S. (1970). "Petrologic history of the moon inferred from petrography, mineralogy and petrogenesis of Apollo 11 rocks". Geochimica et Cosmochimica Acta 34, Supplement 1: 897–925. Bibcode 1970GeCAS...1..897S. doi:10.1016/0016-7037(70)90170-5. 
  13. ^ McCubbina, Francis M.; Steele, Andrew; Haurib, Erik H.; Nekvasilc, Hanna; Yamashitad, Shigeru; Russell J. Hemleya (2010). "Nominally hydrous magmatism on the Moon". Proceedings of the National Academy of Sciences 107 (25): 11223–11228. doi:10.1073/pnas.1006677107. 
  14. ^ Fazekas, Andrew "Moon Has a Hundred Times More Water Than Thought" National Geographic News (June 14, 2010). News.nationalgeographic.com (2010-06-14). Retrieved on 2011-07-24.

Further reading

  • Schmittner Karl-Erich and Giresse Pierre, 1999. Micro-environmental controls on biomineralization: superficial processes of apatite and calcite precipitation in Quaternary soils, Roussillon, France. Sedimentology 46/3: 463–476.

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Look at other dictionaries:

  • Apatite — Catégorie VIII : phosphates, arséniates, vanadates[1] Apatite Québec (Xl 32cm) …   Wikipédia en Français

  • apatite — [ apatit ] n. f. • 1802; d ab. en all.; du gr. apatân « tromper », c. à d. « pierre trompeuse, pseudo précieuse » ♦ Minér. Phosphate de calcium en cristaux ou agrégats, à inclusions fréquentes de chlore (chlorapatiten. f.), de fluor, de silicium… …   Encyclopédie Universelle

  • Apatite — Ap a*tite, n. [Gr. ? deceit, fr. ? to deceive; it having been often mistaken for other minerals.] (Min.) Native phosphate of lime, occurring usually in six sided prisms, color often pale green, transparent or translucent. [1913 Webster] …   The Collaborative International Dictionary of English

  • apatite — s. f. [Mineralogia] Fosfato de cálcio natural.   ♦ Grafia no Brasil: apatita …   Dicionário da Língua Portuguesa

  • apatite — [ap′ə tīt΄] n. [Ger apatit < Gr apatē, deceit + ITE1: so named from being mistaken for other minerals] any of a group of variously colored, hard, hexagonal calcium minerals, Ca5 (PO4, CO3) 3 (F,OH,Cl), found mainly in sedimentary rocks, esp.… …   English World dictionary

  • apatite — /ap euh tuyt /, n. a common mineral, calcium fluorophosphate, Ca5FP3O12, occurring in individual crystals and in masses and varying in color, formerly used in the manufacture of phosphate fertilizers. [1795 1805; < Gk apát(e) trickery, fraud,… …   Universalium

  • apatite — noun /ˈæp.ə.taɪt/ A calcium fluoride phosphate of variable composition, sometimes used in the manufacture of fertilizer. We had prepared, by precipitation methods, finely divided crystalline apatites that were similar in crystal size and x ray… …   Wiktionary

  • apatite — apatitas statusas T sritis chemija apibrėžtis Mineralas. formulė Ca₅[(F,OH)|(PO₄)₃] atitikmenys: angl. apatite rus. апатит …   Chemijos terminų aiškinamasis žodynas

  • apatite — noun Etymology: German Apatit, from Greek apatē deceit Date: 1803 any of a group of calcium phosphate minerals occurring in various colors as hexagonal crystals, as granular masses, or in fine grained masses as the chief constituent of phosphate… …   New Collegiate Dictionary

  • apatite II — a proprietary preparation of fish bones used in removing heavy metals from soil and water. The metals are chemically bound into new minerals that do not dissolve or leach over extremely long time periods …   Dictionary of ichthyology


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