Difference between revisions of "Apatite" - New World Encyclopedia
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| formula = Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>(F,Cl,OH) | | formula = Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>(F,Cl,OH) | ||
| molweight = | | molweight = | ||
| − | | color = [[Transparent]] to [[translucent]], usually green, less often colorless, yellow, blue to violet, pink, brown.<ref name="GRG">[[Gemological Institute of America]], | + | | color = [[Transparent]] to [[translucent]], usually green, less often colorless, yellow, blue to violet, pink, brown.<ref name="GRG">''GIA Gem Reference Guide'' (Carlsbad, CA: [[Gemological Institute of America]], 1995), ISBN 0-87311-019-6.</ref> |
| habit = Tabular, prismatic crystals, massive, compact or granular | | habit = Tabular, prismatic crystals, massive, compact or granular | ||
| system = [[Hexagonal (crystal system)|Hexagonal]] Dipyramidal (6/m)<ref name=Webmineral>[http://webmineral.com/data/Apatite.shtml Apatite Mineral Data.] ''Webmineral.com''. Retrieved May 8, 2007.</ref> | | system = [[Hexagonal (crystal system)|Hexagonal]] Dipyramidal (6/m)<ref name=Webmineral>[http://webmineral.com/data/Apatite.shtml Apatite Mineral Data.] ''Webmineral.com''. Retrieved May 8, 2007.</ref> | ||
| Line 134: | Line 134: | ||
==Gemology== | ==Gemology== | ||
| − | Apatite is infrequently used as a [[gemstone]]. Transparent stones of clean color have been faceted, and [[chatoyant]] specimens have been [[cabochon]] cut.<ref name="GRG"/> Chatoyant stones are known as ''cat's-eye apatite'',<ref name="GRG"/> transparent green stones are known as ''asparagus stone'',<ref name="GRG"/> and blue stones | + | Apatite is infrequently used as a [[gemstone]]. Transparent stones of clean color have been faceted, and [[chatoyant]] specimens have been [[cabochon]] cut.<ref name="GRG"/> Chatoyant stones are known as ''cat's-eye apatite'',<ref name="GRG"/> transparent green stones are known as ''asparagus stone'',<ref name="GRG"/> and blue stones may be called ''[[moroxite]]''.<ref>Edwin W. Streeter, [http://www.farlang.com/gemstones/streeter-precious-stones/page_306/view?searchterm=moroxite Moroxite] ''Precious Stones and Gems'' 6th ed. (London: George Bell and Sons, 1898, p. 306). Retrieved May 8, 2007.</ref> If crystals of rutile have grown in the apatite crystal, the cut stone displays a cat's eye effect when viewed in the right lighting. |
| + | |||
| + | Major sources<ref name="GRG"/> for gem-quality apatite are: [[Brazil]], [[Burma]], and [[Mexico]]. Additional sources include: [[Canada]], [[Czechoslovakia]], [[Germany]], [[India]], [[Madagascar]], [[Mozambique]], [[Norway]], [[South Africa]], [[Spain]], [[Sri Lanka]], and the [[United States]]. | ||
== See also == | == See also == | ||
| Line 171: | Line 173: | ||
* [http://webmineral.com/data/Apatite.shtml Apatite Mineral Data.] ''Webmineral.com''. Retrieved May 8, 2007. | * [http://webmineral.com/data/Apatite.shtml Apatite Mineral Data.] ''Webmineral.com''. Retrieved May 8, 2007. | ||
| − | *[http://webmineral.com/data/Hydroxylapatite.shtml Hydroxylapatite.] ''Webmineral.com''. Retrieved May 8, 2007. | + | *[http://webmineral.com/data/Hydroxylapatite.shtml Hydroxylapatite Mineral Data.] ''Webmineral.com''. Retrieved May 8, 2007. |
| − | * [http://webmineral.com/data/Fluorapatite.shtml Fluoroapatite.] ''Webmineral.com''. Retrieved May 8, 2007. | + | * [http://webmineral.com/data/Fluorapatite.shtml Fluoroapatite Mineral Data.] ''Webmineral.com''. Retrieved May 8, 2007. |
*[http://www.azom.com/details.asp?ArticleID=107 Hydroxyapatite.] ''Azom.com''. Retrieved May 8, 2007. | *[http://www.azom.com/details.asp?ArticleID=107 Hydroxyapatite.] ''Azom.com''. Retrieved May 8, 2007. | ||
Revision as of 19:16, 23 May 2007
<<Check Amethyst Galleries for a broader definition of the Apatite group of minerals.>>
| Apatite | |
|---|---|
 |
|
| General | |
| Category | Phosphate mineral group |
| Chemical formula | Ca5(PO4)3(F,Cl,OH) |
| 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] |
| Luster | Vitreous[1] to subresinous |
| Refractive index | 1.634 - 1.638 (+.012, -.006)[1] |
| Optical Properties | Double refractive, uniaxial negative[1] |
| Birefringence | .002-.008[1] |
| Pleochroism | Blue stones - strong, blue and yellow to colorless. Other colors are weak to very weak.[1] |
| Streak | White |
| Specific gravity | 3.16 - 3.22[2] |
| Diaphaneity | Transparent to translucent[2] |
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, and chlorapatite, named for high concentrations of OH-, F-, or Cl- ions, respectively, in the crystal. The formula of the admixture of the three most common species is written as Ca5(PO4)3(OH, F, Cl), and the formulae of the individual minerals are written as Ca5(PO4)3(OH), Ca5(PO4)3F and Ca5(PO4)3Cl, respectively.
Apatite is one of few minerals that are produced and used by biological micro-environmental systems. Hydroxylapatite is the major component of tooth enamel. A relatively unique 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 that is hydroxyapatite. For this reason, toothpaste typically contain a source of fluoride anions (e.g. sodium fluoride, sodium monofluorophosphate). Similarly, fluoridated water, allow exchange in the teeth of fluoride ions for hydroxy groups in apatite. Too much fluoride results in dental fluorosis and/or skeletal fluorosis.
In the United States, apatite is often used to fertilize tobacco. It partially starves the plant of nitrogen, which gives American cigarettes a different taste from those of other countries.
Fission tracks in apatite are commonly used to determine the thermal history of orogenic (mountain) belts and of sediments in sedimentary basins.
Phosphorite is the name given to impure, massive apatite.
Fluoroapatite
| Fluoroapatite | |
|---|---|
| |
| General | |
| Systematic name | Fluoroapatite |
| Other names | Fluorapatite |
| Molecular formula | Ca5(PO4)3F |
| Molar mass | 504.3 g/mol |
| Appearance | hard solid, various colors |
| CAS number | 68877-08-7 |
| Properties | |
| Solubility in water | almost insoluble |
| Structure | |
| Crystal structure | hexagonal |
| Related compounds | |
| Related compounds | Ca5(PO4)3OH Ca5(PO4)3Cl |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references | |
Fluoroapatite, often with the alternate spelling of fluorapatite, is a mineral with the formula Ca5(PO4)3F (calcium halophosphate). Fluoroapatite is a hard crystalline solid. Although samples can have various color (green, brown, blue, violet, or colorless), the pure mineral is colorless as expected for a material lacking transition metals. It is an important constituent of tooth enamel.[3]
Fluoroapatite crystallizes in a hexagonal crystal system. It is often combined as a solid solution with hydroxylapatite (Ca5(PO4)3OH) in biological matrices. Chloroapatite (Ca5(PO4)3Cl) is another related structure.[3]
Fluoroapatite can be synthesized in a two step process. First, calcium phosphate is generated by combining calcium and phosphate salts at neutral pH.This material then reacts further with fluoride sources (often sodium monofluorophosphate or calcium fluoride (CaF2)) to give the mineral. This reaction is integral in the global phosphorous cycle.[4]
- 3Ca2+ + 2PO43- → Ca3(PO4)2
- 3 Ca3(PO4)2 + CaF2 → 2 Ca5(PO4)3F
Fluoroapatite can also be used as a precursor for the production of phosphorus. The mineral can be reduced by carbon in the presence of quartz, ultimately generating white phosphorus, P4:
- Ca5(PO4)3F + 3SiO2 + 5C → 3CaSiO3 + 5CO + P2
2P2 → P4 after cooling
Hydroxylapatite
Hydroxylapatite, also frequently called hydroxyapatite, is a mineral. It is a naturally occurring form of calcium apatite with the formula Ca5(PO4)3(OH), but is usually written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two molecules. Hydroxylapatite is the hydroxyl endmember of the complex apatite group. The OH- ion can be replaced by fluoride, chloride or carbonate. It crystallizes in the hexagonal crystal system. It has a specific gravity of 3.08 and is 5 on the Mohs hardness scale. Pure hydroxylapatite powder is white. Naturally occurring apatites can however also have brown, yellow or green colorations. Compare to the discolorations of dental fluorosis.
Hydroxylapatite is the main mineral component of bone. Carbonated-calcium deficient hydroxyapatite is the main mineral of which dental enamel and dentin are comprised.
Medical uses
Hydroxylapatite can be used as a filler to replace amputated bone or as a coating to promote bone ingrowth into prosthetic implants. Although many other phases exist with similar or even identical chemical makeup, the body responds much differently to them. Coral skeletons can be transformed into hydroxylapatite by high temperatures; their porous structure allows relatively rapid ingrowth at the expense of initial mechanical strength. The high temperature also burns away any organic molecules such as proteins, preventing host vs. graft disease.
Some modern dental implants are coated with hydroxylapatite. It has been suggested that this may promote osseointegration, but there is not yet conclusive clinical proof of this.
Bioactive Glasses are the only man made materials known to bond to both bone and soft tissue and have been clinically used as a bone grafting material for over 20 years in dental, maxillofacial and orthopedic procedures. The material has been used in both solid form, as a middle ear prosthetic for conducted hearing loss, as well as in particulate form for filling boney defects throughout the body. Unlike hydroxyapatite, which is said to be “osteoconductive” by conducting new bone growth along the materials surface, Bioactive Glasses are “osteostimulative” in that the material stimulates the recruitment and differentiation of osteoblasts which produce new bone. As a result, Bioactive Glass rapidly enhances the production of new bone and is completely resorbed by the body and replaced by new bone. These materials are usually produced in a high temperature (1350 C) melt process but can also be produced by the Sol-Gel process which results in a controlled porosity a resorbability. Bioactive Glasses have also been used in oral care applications as a tooth remineralizer (Calcium Sodium Phosphosilicate) in both professional dental and consumer oral care products.
Hydroxyapatite uses in chromatography
The mechanism of Hydroxyapatite (HAP) chromatography is complicated and has been described as "mixed-mode" ion exchange. It involves nonspecific interactions between positively charged calcium ions and negatively charged phosphate ions on the stationary phase HAP resin with protein negatively charged carboxyl groups and positively charged amino groups. It may be difficult to predict the effectiveness of HAP chromatography based on physical and chemical properties of the desired protein to be purified. For elution, a buffer with increasing phosphate concentration is typically used.
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 may be called moroxite.[5] If crystals of rutile have grown in the apatite crystal, the cut stone displays a cat's eye effect when viewed in the right lighting.
Major sources[1] for gem-quality apatite are: Brazil, Burma, and Mexico. Additional sources include: Canada, Czechoslovakia, Germany, India, Madagascar, Mozambique, Norway, South Africa, Spain, Sri Lanka, and the United States.
See also
Notes
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 GIA Gem Reference Guide (Carlsbad, CA: Gemological Institute of America, 1995), ISBN 0-87311-019-6.
- ↑ 2.0 2.1 2.2 2.3 Apatite Mineral Data. Webmineral.com. Retrieved May 8, 2007.
- ↑ 3.0 3.1 Hurlbert and Klein. "Manual of Mineralogy, 19th Edition." 1977. ISBN 0471251771.
- ↑ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ↑ Edwin W. Streeter, Moroxite Precious Stones and Gems 6th ed. (London: George Bell and Sons, 1898, p. 306). Retrieved May 8, 2007.
ReferencesISBN links support NWE through referral fees
- Farndon, John. 2006. The Practical Encyclopedia of Rocks & Minerals: How to Find, Identify, Collect and Maintain the World's best Specimens, with over 1000 Photographs and Artworks. London: Lorenz Books. ISBN 0754815412.
- Klein, Cornelis, and Barbara Dutrow. 2007. Manual of Mineral Science. 23rd ed. New York: John Wiley. ISBN 978-0471721574.
- Pellant, Chris. 2002. Rocks and Minerals. Smithsonian Handbooks. New York: Dorling Kindersley. ISBN 0789491060.
- Shaffer, Paul R., Herbert S. Zim, and Raymond Perlman. 2001. Rocks, Gems and Minerals. Rev. ed. New York: St. Martin's Press. ISBN 1582381321.
- Mineral Gallery. 2006. The Mineral Apatite. Amethyst Galleries. Retrieved May 8, 2007.
- Mineral Gallery. 2006. The Apatite Group of Minerals. Amethyst Galleries. Retrieved May 8, 2007.
External links
- Apatite. Mindat.org. Retrieved May 8, 2007.
- Apatite Group. Mindat.org. Retrieved May 8, 2007.
- Hydroxylapatite. Mindat.org. Retrieved May 8, 2007.
- Apatite Mineral Data. Webmineral.com. Retrieved May 8, 2007.
- Hydroxylapatite Mineral Data. Webmineral.com. Retrieved May 8, 2007.
- Fluoroapatite Mineral Data. Webmineral.com. Retrieved May 8, 2007.
- Hydroxyapatite. Azom.com. Retrieved May 8, 2007.
- Hydroxylapatite. Center for Advanced Microstructures and Devices, Louisiana State University. Retrieved May 8, 2007.
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