Ruby
43551
225705243
2008-07-15T00:17:33Z
69.12.249.236
/* Historical and cultural references */ Gemstone Ruby was incorrectly associated with the western zodiac sign Cancer, it was corrected to the sign Leo.
{{otheruse|this=the mineral|use1=other uses}}
{{Infobox mineral
| name = Ruby
| category = [[Mineral]] variety
| image = Ruby cristal.jpg
| imagesize = 150
| caption = Ruby crystal before faceting, length 0.8 inches (2 cm)
| formula = [[aluminium oxide]] with [[chromium]], Al<sub>2</sub>O<sub>3</sub>::Cr
| molweight =
| color = Red, may be brownish or purplish
| habit = Varies with locality. Terminated tabular hexagonal prisms.
| system = Trigonal
| twinning =
| cleavage = No true cleavage
| fracture = Uneven or conchoidal
| mohs = 9.0
| luster = Vitreous
| refractive = ~1.762-1.770
| opticalprop =
| birefringence =
| fluorescence= red under longwave
| pleochroism = Orangey red, purplish red
| streak = white
| gravity = 4.0
| melt = 2050°C
| fusibility =
| diagnostic =
| solubility = none
| diaphaneity = transparent
| other =
}}
A '''Ruby''' is a pink to blood red [[gemstone]], a variety of the [[mineral]] [[corundum]] ([[aluminium oxide]]). The common red color is caused mainly by the element [[chromium]]. Its name comes from ''ruber'', [[Latin]] for red. Other varieties of gem-quality corundum are called [[sapphire]]s. It is considered one of the four [[precious stones]], together with the [[sapphire]], the [[emerald]] and the [[diamond]].
Prices of rubies are primarily determined by color. The brightest and best "red" called pigeon blood red, commands a huge premium over other rubies of similar quality. After color follows clarity: similar to diamonds, a clear stone will command a premium, but a ruby without any needle-like [[rutile]] inclusions will indicate the stone has been treated one way or another. Cut and [[Carat (mass)|carat]] (size) also determine the price.
==Physical properties==
Rubies have a [[hardness]] of 9.0 on the [[Mohs scale of mineral hardness]]. Among the natural gems only [[diamond]] is harder, with a Mohs 10.0 by definition.
All natural rubies have imperfections in them, including color impurities and inclusions of [[rutile]] needles known as "silk". Gemologists use these needle inclusions found in natural rubies to distinguish them from synthetics, simulants, or substitutes. Usually the rough stone is heated before cutting. Almost all rubies today are treated in some form, with heat treatment being the most common practice. However, rubies that are completely untreated but still of excellent quality command a large premium.
Some rubies show a 3-point or 6-point [[asterism (gemmology)|asterism]] or ''star''. These rubies are cut into [[cabochons]] to display the effect properly. Asterisms are best visible with a single-light source, and move across the stone as the light moves or the stone is rotated. Such effects occur when light is reflected off the ''silk'' (the structurally oriented [[rutile]] needle. inclusions) in a certain way. This is one example where inclusions increase the value of a gemstone.
Rubies can furthermore show color changes — though this occurs very rarely — and [[chatoyancy]].
==Natural Occurrence==
Rubies are mined in Myanmar (Burma), Thailand, Sri Lanka, Tanzania, Kenya, Madagascar, and Cambodia, but they have also been found in the [[U.S.]] [[U.S. state|states]], in [[Montana]], [[North Carolina]] and [[South Carolina]]. The [[Mogok]] Valley in Upper Myanmar has produced some of the finest rubies, but in recent years very few good rubies have been found there. The unique color in Myanmar (Burmese) rubies is described as "pigeon’s blood". They are known in the trade as “Mogok” rubies. In central Myanmar the area of Mong Hsu also produces rubies. The latest ruby deposit to be found in Myanmar is situated in Nam Ya. In 2002 rubies were found in the Waseges River area of [[Kenya]]. Sometimes [[spinel]]s are found along with rubies in the same rocks and are mistaken for rubies. However, fine red spinels may approach the average ruby in value.<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 |http://books.google.com/books?id=0GAvKQJ2JuwC&pg=RA1-PA541&vq=ruby&source=gbs_search_s&sig=gQ04BI1-64YSwQAQIVkuocr1MLw}}</ref>
[[Image:Cut Ruby.jpg|thumb|right|200px|A cut ruby.<!-- Note that most jewelers would consider this to be very pink for a ruby. Higher quality rubies are a darker red. This stone might even be a pink sapphire.-->]]
The value of natural rubies varies depending on their size, cut, origin, clarity and quality. As of 2000, a gem quality, uncut one carat (0.2 g) ruby cost about $4,200 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&pg=RA1-PA534&vq=ruby&source=gbs_search_s&sig=oglQJX_mgjLvSfm-n1WGHyegDP4}}</ref> As of 2008, an average quality, certified, untreated 1 carat (0.2 g) ruby cost between $800 to $3,500 USD.<ref>{{Citation
| url = http://www.ruby-sapphire.com/r-s-bk-prices.htm
| accessdate = 2008-06-24
}}</ref> Since it is easy to spot synthetic rubies by their lack of natural inclusions, they have not greatly affected the price of natural rubies.<ref>{{Cite book | author=Marfunin, Arnol§d Sergeevich | authorlink= | coauthors= | title=Advanced mineralogy | date=1994 | publisher=Springer-Verlag | location=Berlin | isbn=0-387-58245-2 | pages=428 | url=http://books.google.com/books?id=JyosZ8WbKdEC&pg=PA428&vq=%22synthetic+ruby%22&client=firefox-a&source=gbs_search_s&sig=dyw7ufkzh4GdgUiZgx4FDX-a4jA}}</ref> Synthetic rubies are much less valuable.
==Treatments and enhancements==
Improving the quality of gemstones by treating them is common practice. Some treatments are used in almost all cases and are therefore considered acceptable. During the late 1990s, a large supply of low-cost materials caused a sudden surge in supply of heat-treated rubies, leading to a downward pressure on ruby prices.
Improvements used include color alteration, improving transparency by dissolving rutile inclusions, healing of fractures (cracks) or even completely filling them.
The most common treatment is the application of heat. Most if not all rubies at the lower end of the market are heat treated on the rough stones to improve color, remove ''purple tinge'', blue patches and silk. These heat treatments typically occur around temperatures of 1800°C (3300°F).<ref name="ThemelisRubyHeat">''The Heat Treatment of Ruby and Sapphire.'' Gemlab Inc., Bangkok, Thailand, 1992 | accessdate = 2007-05-28 </ref> Some rubies undergo a process of low tube heat, when the stone is heated over charcoal of a temperature of about 1300°C (2400°F) for 20 to 30 minutes. The silk is only partially broken as the color is improved.
A less acceptable treatment, which has gained notoriety in recent years, is lead glass filling. Filling the fractures inside the ruby with [[lead glass]] dramatically improves the transparency of the stone, making previously unsuitable rubies fit for applications in jewelry. The process is done in four steps:
# The rough stones are pre-polished to eradicate all surface impurities that may affect the process
# The rough is cleaned with [[hydrogen fluoride]]
# The first heating process during which no fillers are added. The heating process eradicates impurities inside the fractures. Although this can be done at temperatures up to 1400°C (2500°F) it most likely occurs at a temperature of around 900°C (1600°F) since the rutile silk is still intact
# The second heating process in an electrical oven with different chemical additives. Different solutions and mixes have shown to be successful, however mostly lead-containing glass-powder is used at present. The ruby is dipped into oils, then covered with powder, embedded on a tile and placed in the oven where it is heated at around 900°C (1600°F) for one hour in an oxidizing atmosphere. The orange colored powder transforms upon heating into a transparent to yellow-colored paste, which fills all fractures. After cooling the color of the paste is fully transparent, that dramatically improves the overall transparency of the ruby.
If a color needs to be added, the glass powder can be "enhanced" with copper or other metal oxides as well as elements such as sodium, calcium, potassium etc.
The second heating process can be repeated three to four times, even applying different mixtures.<ref>{{cite journal| last = Milisenda| first=C C| title=Rubine mit bleihaltigen Glasern gefullt| journal=Zeitschrift der Deutschen Gemmologischen Gesellschaft| volume=54 |issue=1| pages=35–41|publisher=Deutschen Gemmologischen Gesellschaft|date=2005| accessdate = 2007-05-28 }}</ref>
When jewelry containing rubies is heated (for repairs) it should not be coated with boracic acid or any other substance, as this can etch the surface; it does not have to be "protected" like a diamond.
==Synthetic and imitation rubies==
In 1837 Gaudin made the first synthetic rubies by fusing aluminium at a high temperature with a little chromium as a pigment. In 1847 Edelman made white sapphire by fusing alumina in boric acid. In 1877 Frenic and Freil made crystal [[corundum]] from which small stones could be cut. Frimy and [[Auguste Verneuil]] manufactured artificial ruby by fusing BaF<sub>2</sub> and Al<sub>2</sub>O<sub>3</sub> with a little Chromium at red heat. In 1903 Verneuil announced he could produce synthetic rubies on a commercial scale using this [[flame fusion]] process. <ref>{{cite web | url = http://www.farlang.com/gemstones/bahadur_handbook_of_precious_stones/page_067 | title = Bahadur: a Handbook of Precious Stones | date = 1943 | accessdate = 2007-08-19 }}</ref>
Other processes in which synthetic rubies can be produced are through the [[Czochralski process|Pulling process]], flux process, and the [[hydrothermal synthesis|hydrothermal process]]. Most synthetic rubies originate from flame fusion, due to the low costs involved. Synthetic rubies may have no imperfections visible to the naked eye but magnification may reveal curves [[striae]] and gas bubbles. The fewer the number and the less obvious the imperfections, the more valuable the ruby is; unless there are no imperfections (i.e., a "perfect" ruby), in which case it will be suspected of being artificial. [[Dopant]]s are added to some manufactured rubies so they can be identified as synthetic, but most need [[gemmology|gemmological]] testing to determine their origin.
Synthetic rubies have technological uses as well as gemological ones. Rods of synthetic ruby are used to make [[ruby laser]]s and [[maser]]s.
[[Imitation]] rubies are also marketed. Red spinel, red garnet and glass have been falsely named as rubies. Imitations go back to Roman times and already in the 17th century techniques were developed to color foil red -- by burning scarlet wool in the bottom part of the furnace -- which was then placed under the imitation stone. <ref>{{cite web | url = http://www.farlang.com/gemstones/nicols-history-gemstones/page_036 | title = Thomas Nicols: A Lapidary or History of Gemstones | date = 1652 | accessdate = 2007-08-19 }}</ref>
Trade terms such as [[balas ruby]] for red spinel and [[rubellite]] for red [[tourmaline]] can mislead unsuspecting buyers. Such terms are therefore discouraged from use by many gemological associations such as the Laboratory Manual Harmonisation Committee (LMHC).
==Records==
<!-- Deleted image removed: [[Image:Carmen lucia ruby side.jpg|150px|thumb|right|The Carmen Lúcia Ruby at The Smithsonian's [[National Museum of Natural History]].]] -->
*Although pieces of red corundum can be found weighing many kilograms, they are generally not of sufficient quality to be valuable as gemstones. For this reason, auction prices are the best indicator of a stone's true value, and prices do not necessarily correlate with size. As of 2006, the record price paid at auction for a single stone was $5,860,000 for an unnamed 38.12 carat cabochon-cut ruby.<ref>{{cite web |url=http://www.ruby-sapphire.com/r-s-bk-quality5.htm |title=Judging Quality: A Connoisseur's Guide |accessdate=2007-01-31 |last=Hughes |first=Richard |date=2006-04-26 |format=HTML |work=Ruby & Sapphire}}</ref>
*The Smithsonian's [[National Museum of Natural History]] in Washington DC, has received one of the world's largest and finest ruby gemstones. The spectacular 23.1-carat Burmese ruby, set in a platinum ring with diamonds, was donated by businessman and philanthropist Peter Buck in memory of his wife Carmen Lúcia. This extraordinary gemstone displays a richly saturated red color combined with an exceptional transparency. The finely proportioned cut provides vivid red reflections. The stone was mined from the famous [[Mogok]] region of [[Burma]] (now [[Myanmar]]) in the 1930s.<ref>{{cite web |url=http://www.mnh.si.edu/exhibits/ruby/index.htm |title=The Carmen Lúcia Ruby |accessdate=2008-02-28 |format=HTML |work=Exhibitions}}</ref>
==Historical and cultural references==
* According to [[Bahya ben Asher|Rebbenu Bachya]], and the [[New International Version]], the word ''odem'' means "ruby" in the verse [[Exodus]] 28:17 (referring to a stone on the [[Hoshen]]), and was the stone representing the tribe of [[Reuben]]. Modern [[Hebrew language|Hebrew]] has taken this meaning. However, ''odem'' actually means ''earth'', and is [[cognate]] with ''[[Adam (name)|Adam]]''; in the Middle East, the earth it refers to is certainly reddish, but the [[Septuagint]] translates the term as [[sard]] (which also means red), which is also the name of a common, somewhat opaque, gem. Scholars think the stone intended is probably a sard, as does the [[King James Version]], scholars think that if not a sard it may possibly be the related gem [[carnelian]]; it is thought possible that ''sard'' and ''odem'' here just mean the colour of the stone, and red [[jasper]] would therefore also be a possibility.
* Ruby is the most commonly named precious stone in English translations of the Bible; an example being [[Book of Proverbs|Proverbs]] 31: "''A virtuous wife is more precious than rubies.''". The underlying [[masoretic text]] doesn't necessarily refer to rubies, however. Not only are there issues such as that mentioned with ''odem'', but in the case of Proverbs 31, the masoretic text merely states ''jewels'', and the [[Septuagint]] makes Proverbs 31 refer to ''precious stones'' (''estin lithon'' ); some English versions of the bible believe that ''pearls'' is a better translation here.
* An early recorded note of the transport and trading of rubies arises in the literature on the [[North Silk Road]] of China, where in about 100 [[Before Christ|BC]] rubies were carried along this ancient [[trackway]] moving westward from China.<ref>[http://www.megalithic.co.uk/article.php?sid=18006 C.Michael Hogan,''Silk Road, North China'', The Megalithic Portal, ed. A. Burnham]</ref>
* The famous lighted "[[Kremlin stars|Red Stars]]" mounted above [[Kremlin]] spires, thought to be giant rubies mined in [[Siberia]], are colored glass.
* Ruby is the [[Birthday#Birthstones|birthstone]] associated with July and of the zodiac sign [[Leo (astrology)|Leo]].
* Ruby is associated with the sun in [[Vedic astrology]].
* Ruby is associated with a 40th [[wedding anniversary]].
* Rubies have always been held in high esteem in Asian countries. They were used to ornament armor, scabbards, and harnesses of noblemen in India and China. Rubies were laid beneath the foundation of buildings to secure good fortune to the structure.<ref name=smith>{{cite book | last = Smith | first = Henry G. | title = Gems and Precious Stones | publisher = Charles Potter Government Printer, Australia | year = 1896}} URL:[http://www.farlang.com/gemstones/smith-gems-prec-stones/page_028 Chapter 2, Sapphires, Rubies]</ref>
==Valley of rubies==
Of the world's rubies, 90% currently derive from [[Myanmar]] (Burma) whose red stones are prized for their [[purity]] and [[hue]]. [[Thailand]] buys the majority of Myanmar's [[gems]]. Myanmar's "''Valley of Rubies''", the mountainous [[Mogok]] area, 200 km (125 miles) north of [[Mandalay]], is noted for its rare pigeon's blood rubies and blue [[sapphires]]. But working conditions in the mines are horrendous. Debbie Stothard of the Alternative [[ASEAN]] Network on [[Burma]] stated that mining operators used drugs on employees to improve productivity, with needles shared, raising the risk of [[HIV]] infection: "''These rubies are red with the blood of young people''." Brian Leber (41-year-old jeweler who founded The Jewellers' Burma Relief Project) stated that: "''For the time being, Burmese gems should not be something to be proud of. They should be an object of revulsion. It's the only country where one obtains really top quality rubies, but I stopped dealing in them. I don't want to be part of a nation's misery. If someone asks for a ruby now I show them a nice pink sapphire''."<ref>[http://features.us.reuters.com/cover/news/MAN51776.html Reuters, Move over, blood diamonds]</ref> In 2007, following the [[2007 Burmese anti-government protests|crackdown on pro-democracy protests in Myanmar]], human rights organizations, gem dealers, and US First Lady [[Laura Bush]] called for a boycott of a Myanmar gem auction held twice yearly, arguing that the sale of the stones profits the dictatorial regime in that country. <ref>[http://www.cbc.ca/consumer/story/2007/11/19/rubies.html CBC - Gem dealers push to ban Burmese rubies after bloody crackdown]</ref>
==See also==
{{commonscat}}
* [[List of minerals]]
==References==
{{reflist}}
==External links==
*[http://www.gemstone.org/gem-by-gem/english/ruby.html International Colored Stone Association's ruby overview page]
*[http://webmineral.com/data/Corundum.shtml Webmineral crystallographic and mineral info]
*[http://www.farlang.com/gemstones/rubies Farlang's Historical references on rubies]: mining, famous rubies etc.
*[http://www.mindat.org/min-3473.html Mindat Ruby localities]
{{Jewellery Materials}}
[[Category:Gemstones]]
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