Sapphire
29469
225610213
2008-07-14T15:24:14Z
Caiaffa
905389
Reverted 1 edit by [[Special:Contributions/81.111.144.3|81.111.144.3]] identified as [[WP:VAND|vandalism]] to last revision by [[User:Melesse|Melesse]]. ([[WP:TW|TW]])
{{Refimprove|date=March 2008}}
{{Mergefrom | padparadscha | Talk:Sapphire#Proposed Merger with Padparadscha|date=September 2007}}
{{otheruses}}
{{Infobox mineral
| name = Sapphire
| category = [[Mineral]] Variety
| boxwidth =
| boxbgcolor =
| image = SaphirSynthetique.jpg
| imagesize =
| caption =
| formula = [[aluminium oxide]], Al<sub>2</sub>O<sub>3</sub>
| molweight =
| color = Every color except red (which is [[ruby]])
| habit = massive and granular
| system = Hexagonal
| twinning =
| cleavage = None
| fracture = Conchoidal, splintery
| mohs = 9.0
| luster = Vitreous
| refractive = 1.762-1.778
| opticalprop = [[Abbe number]] 72.2
| birefringence = 0.008
| pleochroism = Strong
| streak = White
| gravity = 3.95-4.03
| density =
| melt = 2030 - 2050 °C
| fusibility = infusible
| diagnostic =
| solubility = insoluble
| diaphaneity =
| other = [[Coefficient of thermal expansion]] 5e-6–6.6e-6/K
}}
'''Sapphire''' refers to gem varieties of the mineral [[corundum]], an [[aluminium oxide]] (Al<sub>2</sub>O<sub>3</sub>), when it is a color other than red. Sapphire can be found naturally or manufactured in large crystal [[boule (crystal)|boules]]. Because of its remarkable hardness sapphire is used in many applications, including [[infrared]] optical components, watch crystals, high-durability windows, and [[Wafer (electronics)|wafer]]s for the deposition of semiconductors, such as [[GaN]] [[nanorods]].
The mineral corundum consists of pure aluminium oxide. Trace amounts of other elements such as [[iron]], [[titanium]] and [[chromium]] give corundum their blue, yellow, pink, purple, orange or greenish color. Sapphire includes any gemstone quality varieties of the mineral corundum except the fully saturated red variety, which is instead known as [[ruby]], and the pinkish-orange variety known as [[padparadscha]].
==Natural sapphire==
Sapphires and rubies are formed at great depth in the earth's mantle or the lowest part of the crust<ref>Understanding the origin of rubies and sapphires to improve prospecting strategies http://www.eurekalert.org/pub_releases/2007-12/idrp-uto120307.php</ref>. Although blue is considered the ''normal'' color for sapphires, they can be found across a full range of spectral colors as well as brown, colorless, grey and black. Those other than blue in color are considered ''fancy color'' sapphires. Some natural sapphires can be found as completely transparent, or "white." White sapphires usually come out of the ground as light grey or brown and are then heated to make them clear. However, in very rare circumstances they will be found in a clear state.
The cost of sapphire gems varies depending on their color, clarity, size, cut, and overall quality. As of 2000, the cost of 1 carat (0.2 g) of a typical uncut, gem quality sapphire was about $1,600 USD.<ref>{{Cite book | author=Wenk, Hans-Rudolf; Bulakh, A. G. | authorlink= | coauthors= | title=Minerals: their constitution and origin | date=2004 | publisher=Cambridge University Press | location=Cambridge, U.K. | isbn=0-521-52958-1 | pages=534 |url=http://books.google.com/books?id=0GAvKQJ2JuwC&printsec=frontcover#PRA1-PA534,M1}}</ref> Significant sapphire deposits are found in Eastern Australia, Southeast Asia, and Sri Lanka. Sapphire and rubies are often found together in the same area, but one gem is usually more abundant.<ref>{{Cite book | author=Wenk, Hans-Rudolf; Bulakh, A. G. | authorlink= | coauthors= | title=Minerals: their constitution and origin | date=2004 | publisher=Cambridge University Press | location=Cambridge, U.K. | isbn=0-521-52958-1 | pages=539-541 |url=http://books.google.com/books?id=0GAvKQJ2JuwC&pg=RA1-PA539&vq=sapphire&source=gbs_search_s&sig=m_o9AxN7Wr0_Zmm7bCOFs7zsW2Y}}</ref>
===Blue sapphire===
[[Image:logansapphire.jpg|right|thumb|150px|The 422.99-carat [[Logan sapphire]], [[National Museum of Natural History]], Washington D.C. It is one of the largest faceted gem-quality blue sapphires in the world.]]
Various shades of blue [dark and light] result from [[titanium]] and [[iron]] substitutions in the aluminum oxide [[crystal lattice]]. Some stones are not well saturated and show tones of Grey. It is common practice to bake natural sapphires to improve or enhance color. This is usually done by heating the sapphires to temperatures of up to 1800 °C for several hours, or by heating in a nitrogen deficient atmosphere oven for seven days or more. On magnification, the ''silk'' due to included [[rutile]] needles are often visible. If the needles are unbroken, then the stone was not heated; if the ''silk'' is not visible then the stone was heated adequately. If the ''silk'' is partially broken, then a process known as low tube heat may have been used. Low tube heat is the process whereby the rough stone is heated to 1300 °C over charcoal for 20 to 30 minutes. This removes grey or brown in the stone and improves color saturation.
===Fancy color sapphire===
Purple sapphires are lower in price than blue ones. These stones contain the trace element [[vanadium]] and come in a variety of shades. Yellow and green sapphires have traces of iron that gives them their color. Pink sapphires have a trace of the element [[chromium]] and the deeper the color pink the higher their monetary value as long as the color is going toward the red of rubies. Sapphires also occur in shades of orange and brown, and colorless sapphires are sometimes used as diamond substitutes in jewelry. Salmon-color [[padparadscha]] sapphires often fetch higher prices than many of even the finest blue sapphires. The word 'padparadscha' is [[Sinhalese language|Sinhalese]] for 'lotus flower'. Recently many sapphires of this color have appeared on the market as a result of a new treatment method called "lattice diffusion".{{Fact|date=April 2007}}
===Color change sapphire===
Color shift sapphires are blue in outdoor light and purple under [[incandescent]] indoor light. Color changes may also be pink in daylight to greenish under fluorescent light. Some stones shift color well and others only partially, in that some stones go from blue to bluish purple. Such color-change sapphires are widely sold as “lab” or “synthetic” alexandrite, which is accurately called an alexandrite simulant (also called alexandrium) since the latter is actually a type of [[chrysoberyl]]---an entirely different substance whose pleochroism is different and much more pronounced than color-change corundum (sapphire).
===Star sapphire===
[[Image:Star-Saphire.jpg|right|thumb|150px|The 182 carat (36.4 g) Star of Bombay, housed in the [[National Museum of Natural History]], Washington D.C., is a good example of a blue star sapphire.]]
A '''star sapphire''' is a type of sapphire that exhibits a star-like phenomenon known as [[asterism (gemmology)|asterism]]. Star sapphires contain intersecting needle-like inclusions (often the mineral [[rutile]], a mineral composed primarily of [[titanium dioxide]]<ref name="BuildingBlocks451-3">{{cite book |last=Emsley |first=John |title=Nature's Building Blocks: An A-Z Guide to the Elements |year=2001 |id=ISBN 0-19-850341-5 |pages=pp. 451 – 53 |publisher=[[Oxford University Press]] |location=Oxford}}</ref> ) that cause the appearance of a six-rayed 'star'-shaped pattern when viewed with a single overhead light source.
The value of a star sapphire depends not only on the [[carat (mass)|carat]] weight of the stone but also the body color, visibility and intensity of the asterism.
===Treatments===
Some sapphires are heat-treated or otherwise enhanced to improve their appearance and color, though some people object to such practices and prefer natural untreated stones. Heat treatments tend to improve the sapphire's color and clarity, and it is unusual to find un-heated stones for sale. Controversy has arisen as certain milky white sapphire stones, called [[geuda]], can obtain clear blue color after heat treatment, dramatically increasing the appearance and value of an otherwise nearly worthless gem. Diffusion treatments are somewhat more controversial as they are used to add elements to the sapphire for the purpose of improving colors.
===Mining===
[[Image:1szafir_Madagaskar.jpg|thumb| A sapphire from Madagascar.]]
Sapphires are mined from [[alluvium|alluvial]] deposits or from primary underground workings. The finest specimens are mined in the disputed territory of [[Kashmir]], [[Myanmar]], [[Madagascar]] and [[Sri Lanka]]. Both the [[Logan sapphire]] and the [[Star of Bombay]] originate from Sri Lankan mines. Sapphires are also mined in [[Australia]], [[Thailand]] and [[China]]. Madagascar leads the world in sapphire production (as of 2007) specifically in and around the city of [[Ilakaka]]. Prior to Ilakaka, Australia was the largest producer of sapphires (as of 1987). Ilakaka is prone to violence, but sapphires are found everywhere including on the ground and in the river mud. [[Pakistan]], [[Afghanistan]], [[India]], [[Tanzania]] and [[Kenya]] also produce sapphires, and less commercially-significant deposits are found in many other countries. The US state of [[Montana]] has produced sapphires from both the El Dorado Bar and Spokane Bar deposit near [[Helena, Montana|Helena]]. Well-known for their intense, pure blue color, yogo sapphires are found in Yogo Gulch, near Utica, Montana. Gem grade sapphires and rubies are also found in and around Franklin, North Carolina, USA. Several mines are open to the public.
==Synthetic sapphire==
[[Image:Labstarsapphirering.JPG|right|thumb|A synthetic star sapphire in a silver ring.]]
In 1902, French chemist [[Auguste Verneuil]] developed a process for growing synthetic sapphire crystals.<ref>M.A. Verneuil (September 1904) Memoire sur la reproduction artificielle du rubis per fusion, ''Annales de Chimie et de Physique''</ref> In the [[Verneuil process]], fine [[alumina]] powder is added to an oxyhydrogen flame which is directed against a mantle.<ref>Heaton, Neal; ''The production and identification of artificial precious stones'' in {{cite book
| last =
| first =
| authorlink =
| coauthors =
| title = Annual Report of the Board of Regents of the Smithsonian Institution, 1911
| publisher = Government Printing Office
| date = 1912
| location = USA
| pages = p.217
| url = http://books.google.com/books?id=hZIKAAAAIAAJ&pg=PA227
| doi =
| id =
| isbn = }}</ref> Alumina in the flame is slowly deposited, creating a teardrop shaped '[[boule (crystal)|boule]]' of sapphire. Chemical dopants can be added to create artificial versions of ruby and all the other sapphire gems, plus colors never seen in nature. Artificial sapphire is identical to natural sapphire, except it can be made without the flaws found in natural stones. Many methods of manufacturing sapphire today are variations of the [[Czochralski process]], invented in 1916.<ref>{{cite web
| last = Ramdeva
| first = Ardamun
| authorlink =
| coauthors =
| title = Synthetic Sapphires
| work = Gemstones
| publisher = JewelInfo4You
| date = 2004
| url = http://www.jewelinfo4u.com/Synthetic_sapphires.aspx
| format =
| doi =
| accessdate = 2008-07-04}}</ref> A tiny sapphire seed crystal is dipped into a crucible of molten alumina and slowly withdrawn upward at a rate of 1 to 100 mm per hour. The alumina crystallizes on the end, creating long carrot shaped [[boule (crystal)|boule]]s of large size, up to 400 mm in diameter and weighing almost 500 kg.<ref name=scheel/>
As of 2003, the world's production capacity of synthetic sapphire is 250 tons.(1.25 x 10<sup>9</sup>carats).<ref name=scheel/> The availability of cheap synthetic sapphire unlocked many industrial uses for this unique material:
The first [[laser]] was made with a rod of synthetic ruby. [[Ti-sapphire laser]] is popular due to the relatively rare ability to tune the laser wavelength in the red-to-near [[infrared]] region of the [[electromagnetic spectrum]]. It can also be easily [[modelocking|modelocked]]. In these lasers, a synthetically produced sapphire [[crystal]] with chromium or [[titanium]] impurities is irradiated with intense light from a special lamp, or another laser, to create [[stimulated emission]].
One application of synthetic sapphire is ''sapphire glass''. Sapphire is not only highly transparent to wavelengths of light between 170 nm to 5.3 μm (the human eye can discern wavelengths from around 400 nm to 700 nm), but it is also five times stronger than glass and ranks a 9 on the [[Mohs Scale]], although it is also more brittle. Sapphire glass is made from pure sapphire boules by slicing off and polishing thin wafers. Sapphire glass windows are used in high pressure chambers for [[spectroscopy]], crystals in high quality [[watch|watches]], and windows in grocery store [[barcode scanner]]s since the material's exceptional hardness makes it very resistant to scratching.<ref name=scheel>{{Cite book | author=Scheel, Hans Jr̲g; Fukuda, Tsuguo | authorlink= | coauthors= | title=Crystal growth technology | date=2003 | publisher=J. Wiley | location=Chichester, West Sussex | isbn=0-471-49059-8 | pages= | url=http://media.wiley.com/product_data/excerpt/98/04714905/0471490598.pdf | format =PDF}}</ref> Owners of such watches should still be careful to avoid exposure to [[diamond]] jewelry, and should avoid striking their watches against artificial stone and simulated stone surfaces that often contain [[silicon carbide]] and other materials that are harder than sapphire and thus capable of causing scratches.
Wafers of single crystal sapphire are also used in the [[semiconductor]] industry as a [[Wafer (electronics)|substrate]] for the growth of [[gallium nitride]] based devices.
[[Image:cermax.jpg|thumb|300px|Cermax xenon arc lamp with synthetic sapphire output window]]
One type of [[xenon arc lamp]], known as Cermax (original brand name - generically known as a ceramic body xenon lamp), uses sapphire output windows that are doped with various other elements to tune their emission. In some cases, the UV emitted from the lamp during operation causes a blue glow from the window after the lamp is turned off. It is approximately the same color as [[Cherenkov radiation]] but is caused by simple [[phosphorescence]].
A transparent conductive coating (TCC) formed from gallium nitride GaN on a sapphire substrate. In order to account for the lattice mismatch between the GaN and the sapphire substrate, a nucleation layer is formed on the sapphire substrate. A mask, for example, silicon dioxide SiO2, is formed on top of the nucleation layer with a plurality of openings. GaN is grown through the openings in the mask to form a lateral epitaxial overgrowth layer upon which defect-free GaN is grown. The lateral epitaxial overgrowth compensates for the lattice mismatch between the sapphire substrate and the GaN. The use of a sapphire substrate eliminates the need for a cover glass and also significantly reduces the cost of the TCC, since such sapphire substrates are about {fraction (1/7)} the cost of germanium substrates. The TCC may then be disposed on a GaAs solar cell. In order to compensate for the lattice mismatches between the GaAs and the GaN, an indium gallium phosphate InGaP may be disposed between the GaAs solar cell and the GaN TCC to compensate for the lattice mismatch between the GaN and the GaAs. In order to further compensate for the lattice mismatch between the GaN and InGaP, the interface may be formed as a super lattice or as a graded layer. Alternatively, the interface between the GaN and the InGaP may be formed by the offset method or by wafer fusion. The TCC, in accordance with the present invention, is able to compensate for the lattice mismatches at the interfaces of the TCC while eliminating the need for a cover glass and a relatively expensive germanium substrate.
==Historical and cultural references==
*According to [[Bahya ben Asher|Rebbenu Bachya]], and many English Bible translations, the word ''Sapir'' in the verse [[Exodus]] 28:18 means ''sapphire'' and was the stone on the [[Ephod]] representing the tribe of [[Issachar]]. However, this is extremely disputed as though it is true that the English word ''sapphire'' derives from the Hebrew ''sapir'' (via Greek ''sapphiros''), sapphires were actually not known before the Roman Empire (and were initially considered to be forms of [[jacinth]], rather than deserving of a word to themselves), and prior to that time ''sapphiros'' referred to blue gems in general. It is thought by scholars that the ''sapphire'' of the Bible was actually [[lapis lazuli]] - which was frequently sent as a gift between middle-eastern nations in Biblical times (Texas Natural Science Center, 2006). There is a wide range of views among traditional sources about which tribe the stone refers to.
*Blue sapphire is associated with Saturn (Wojtilla, 1973), yellow sapphire with Jupiter in [[Vedic astrology]]. It is understood that word Sapphire seems to be a corrupted form of ''Sanipriya''([[Sanskrit]]:- ''Sani'' = [[Saturn]], ''Priya'' = [[Beloved]]). [[Buddhist]] monks who moved to [[Middle East]] introduced the Stone as ''Sani piriya'' and eventually become ''sapir'' and ''sapphire''.
*Sapphire is the [[birthstone]] associated with September.
*The 45th [[wedding anniversary]] is known as the sapphire anniversary.
The theft of a sapphire known as the "Blue Water" is central to the plot of the novel [[Beau Geste]] by P. C. Wren and its various film adaptations.
==References==
{{commonscat|Sapphire}}
{{reflist}}
* Wojtilla, G. Indian precious stones in the ancient East and West, Acta Orientakia (Budapest) 27, 2, 211-224.
* Sofianides, Anna S. and George E. Harlow, 1997, ''Gems & Crystals'', Parkgate Books, pp. 44-55 ISBN 1-85585-391-4
*[http://www.utexas.edu/tmm/npl/mineralogy/Lore_and_Mythology/index.htm Texas Natural Science Center], ''Mineral Lore and Mythology'', 2006
*[http://webmineral.com/data/Corundum.shtml Wedmineral Corundum Page] Webmineral with extensive crystallographic and mineralogical information on Corundum
*[http://www.farlang.com/gemstones/sapphires Farlang Sapphire References] Historical resources on Sapphires, mining, famous gems etc.
*[http://www.mindat.org/min-3529.html Mindat Sapphire page] Mindat with extensive locality information
*[http://www.gemstone.org/gem-by-gem/english/sapphire.html ICA's Sapphire page] International Colored Stone Sapphire page
{{Jewellery Materials}}
[[Category:Gemstones]]
[[Category:Oxide minerals]]
[[Category:Optical materials]]
[[Category:Dielectrics]]
[[Category:Transparent materials]]
[[bg:Сапфир]]
[[cs:Safír]]
[[da:Safir]]
[[de:Saphir]]
[[et:Safiir]]
[[el:Ζαφείρι]]
[[es:Zafiro]]
[[eo:Safiro]]
[[eu:Zafiro]]
[[fr:Saphir]]
[[hi:नीलम]]
[[id:Safir]]
[[it:Zaffiro]]
[[he:ספיר]]
[[la:Sapphirus]]
[[lv:Safīrs]]
[[lt:Safyras]]
[[nl:Saffier]]
[[ja:サファイア]]
[[no:Safir]]
[[pl:Szafir]]
[[pt:Safira]]
[[ro:Safir]]
[[ru:Сапфир]]
[[simple:Sapphire]]
[[sk:Zafír]]
[[sl:Safir]]
[[fi:Safiiri]]
[[sv:Safir]]
[[te:నీలమణి]]
[[vi:Xa-phia]]
[[tr:Safir]]
[[uk:Сапфір]]
[[zh:蓝宝石]]