Ruby - Wikipedia Ruby This article is about the mineral or gem. For other uses, see Ruby ( disambiguation ). Ruby Natural ruby crystals from Winza, Tanzania General Oxide mineral variety Formula ( repeating unit ) aluminium oxide with chromium, Al O : Cr Crystal system Trigonal Crystal class Hexagonal scalenohedral ( 3m ) H-M symbol : ( 3 2 / m ) Space group R3c Identification Color Near colorless through pink through all shades of red to a deep crimson Crystal habit Terminated tabular hexagonal prisms. Cleavage No true cleavage Fracture Conchoidal, splintery Tenacity Brittle Mohs scale hardness 9.0 Luster Subadamantine, vitreous, pearly ( on partings ) Streak white Diaphaneity transparent, translucent Specific gravity 3.97 -- 4.05 Optical properties Uniaxial - Refractive index n = 1.768 -- 1.772 n = 1.760 -- 1.763 Birefringence 0.008 Pleochroism Strong : purplish - red -- orangy - red Dispersion 0.018 Ultraviolet fluorescence red under longwave References A ruby is a pink to blood - red colored gemstone, a variety of the mineral corundum ( aluminium oxide ). Other varieties of gem - quality corundum are called sapphires. Ruby is one of the traditional cardinal gems, together with amethyst, sapphire, emerald, and diamond. The word ruby comes from ruber, Latin for red. The color of a ruby is due to the element chromium. The quality of a ruby is determined by its color, cut, and clarity, which, along with carat weight, affect its value. The brightest and most valuable shade of red called blood - red or pigeon blood, commands a large 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 may indicate that the stone has been treated. Ruby is the traditional birthstone for July and is usually more pink than garnet, although some rhodolite garnets have a similar pinkish hue to most rubies. The world 's most expensive ruby is the Sunrise Ruby. Contents 1 Physical properties 1.1 Ruby vs. pink sapphire 2 Natural occurrence 3 Factors affecting value 4 Treatments and enhancements 5 Synthetic and imitation rubies 6 Records and famous rubies 7 Historical and cultural references 8 See also 9 References 10 External links Physical properties Crystal structure of rubies Rubies have a hardness of 9.0 on the Mohs scale of mineral hardness. Among the natural gems only moissanite and diamond are harder, with diamond having a Mohs hardness of 10.0 and moissanite falling somewhere in between corundum ( ruby ) and diamond in hardness. Sapphire, ruby, and pure corundum are α - alumina, the most stable form of Al O, in which 3 electrons leave each aluminum ion to join the regular octahedral group of six nearby O ions ; in pure corundum this leaves all of the aluminum ions with a very stable configuration of no unpaired electrons or unfilled energy levels, and the crystal is perfectly colorless. When a chromium atom replaces an occasional aluminum atom, it too loses 3 electrons to become a chromium ion to maintain the charge balance of the Al O crystal. However, the Cr ions are larger and have electron orbitals in different directions than aluminum. The octahedral arrangement of the O ions is distorted, and the energy levels of the different orbitals of those Cr ions are slightly altered because of the directions to the O ions. Those energy differences correspond to absorption in the ultraviolet, violet, and yellow - green regions of the spectrum. Transmittance of ruby in optical and near - IR spectra. Note the two broad violet and yellow - green absorption bands and one narrow absorption band at the wavelength of 694 nm, which is the wavelength of the ruby laser. If one percent of the aluminum ions are replaced by chromium in ruby, the yellow - green absorption results in a red color for the gem. Additionally, absorption at any of the above wavelengths stimulates fluorescent emission of 694 - nanometer - wavelength red light, which adds to its red color and perceived luster. After absorbing short - wavelength light, there is short interval of time when the crystal lattice of ruby is in an excited state before fluorescence occurs. If 694 - nanometer photons pass through the crystal during that time, they can stimulate more fluorescent photons to be emitted in - phase with them, thus strengthening the intensity of that red light. By arranging mirrors or other means to pass emitted light repeatedly through the crystal, a ruby laser in this way produces a very high intensity of coherent red light. 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. These days, almost all rubies are treated in some form, with heat treatment being the most common practice. Untreated rubies of high quality command a large premium. Some rubies show a three - point or six - point 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. Furthermore, rubies can show color changes -- though this occurs very rarely -- as well as chatoyancy or the `` cat 's eye '' effect. Ruby vs. pink sapphire Generally, gemstone - quality corundum in all shades of red, including pink, are called rubies. However, in the United States, a minimum color saturation must be met to be called a ruby ; otherwise, the stone will be called a pink sapphire. Drawing a distinction between rubies and pink sapphires is relatively new, having arisen sometime in the 20th century. Often, the distinction between ruby and pink sapphire is not clear and can be debated. As a result of the difficulty and subjectiveness of such distinctions, trade organizations such as the International Colored Gemstone Association ( ICGA ) have adopted the broader definition for ruby which encompasses its lighter shades, including pink. Natural occurrence The Mogok Valley in Upper Myanmar ( Burma ) was for centuries the world 's main source for rubies. That region has produced some very fine rubies, but in recent years few good rubies have been found there. In central Myanmar, the area of Mong Hsu began producing rubies during the 1990s and rapidly became the world 's main ruby mining area. The most recently found ruby deposit in Myanmar is in Namya ( Namyazeik ) located in the northern state of Kachin. Historically, rubies have also been mined in Thailand, in the Pailin and Samlout District of Cambodia, as well as in Afghanistan, Australia, Brazil, Colombia, India, Namibia, Japan, and Scotland ; after the Second World War ruby deposits were found in Madagascar, Nepal, Pakistan, Tajikistan, Tanzania, and Vietnam. In Sri Lanka, lighter shades of rubies ( often `` pink sapphires '' ) are more commonly found. Republic of Macedonia is the only country in mainland Europe to have naturally occurring rubies. They can mainly be found around the city of Prilep. Macedonian ruby has a unique raspberry color. The ruby is also included on the Macedonian Coat of Arms. A few rubies have been found in the U.S. states of Montana, North Carolina, South Carolina and Wyoming. Spinel, another red gemstone, is sometimes found along with rubies in the same gem gravel or marble. Red spinel may be mistaken for ruby by those lacking experience with gems. However, the finest red spinels can have a value approaching that of the average ruby. Factors affecting value Rubies, as with other gemstones, are graded using criteria known as the four Cs, namely color, cut, clarity and carat weight. Rubies are also evaluated on the basis of their geographic origin. Color : In the evaluation of colored gemstones, color is the most important factor. Color divides into three components : hue, saturation and tone. Hue refers to color as we normally use the term. Transparent gemstones occur in the pure spectral hues of red, orange, yellow, green, blue, violet. In nature, there are rarely pure hues, so when speaking of the hue of a gemstone, we speak of primary and secondary and sometimes tertiary hues. Ruby is defined to be red. All other hues of the gem species corundum are called sapphire. Ruby may exhibit a range of secondary hues, including orange, purple, violet, and pink. A naturally occurring ruby crystal Natural ruby with inclusions A cut pink ruby Purple rubies Victorian ruby and diamond brooch The finest ruby is described as being a vivid medium - dark toned red. Secondary hues add an additional complication. Pink, orange, and purple are the normal secondary hues in ruby. Of the three, purple is preferred because it reinforces the red, making it appear richer. Purple also occupies a position on the color wheel halfway between red and blue. When a purplish - red ruby is set in yellow, the yellow neutralizes its complement blue, leaving the stone appearing to be pure red in the setting. 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 rubies at the lower end of the market are heat treated to improve color, remove purple tinge, blue patches, and silk. These heat treatments typically occur around temperatures of 1800 ° C ( 3300 ° F ). 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 partially broken, and the color is improved. Another treatment, which has become more frequent in recent years, is lead glass filling. Filling the fractures inside the ruby with lead glass ( or a similar material ) 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 and 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. 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. The treatment can identified by noting bubbles in cavities and fractures using a 10x loupe. Synthetic and imitation rubies Artificial ruby under a normal light ( top ) and under a green laser light ( bottom ). Red light is emitted In 1837, Gaudin made the first synthetic rubies by fusing potash alum at a high temperature with a little chromium as a pigment. In 1847, Ebelmen 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 and Al O 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. By 1910, Verneuil 's laboratory had expanded into a 30 furnace production facility, with annual gemstone production having reached 1,000 kilograms ( 2,000 lb ) in 1907. Other processes in which synthetic rubies can be produced are through Czochralski 's pulling process, flux process, and the 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. Dopants are added to some manufactured rubies so they can be identified as synthetic, but most need gemological testing to determine their origin. Synthetic rubies have technological uses as well as gemological ones. Rods of synthetic ruby are used to make ruby lasers and masers. The first working laser was made by Theodore H. Maiman in 1960. Maiman used a solid - state light - pumped synthetic ruby to produce red laser light at a wavelength of 694 nanometers ( nm ). Ruby lasers are still in use. Rubies are also used in applications where high hardness is required such as at wear exposed locations in modern mechanical clockworks, or as scanning probe tips in a coordinate measuring machine. Imitation rubies are also marketed. Red spinels, red garnets, and colored glass have been falsely claimed to be 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. 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 and famous rubies Rubies at the National Museum of Natural History, Washington, D.C., USA The Smithsonian 's National Museum of Natural History in Washington, D.C. has some of the world 's largest and finest ruby gemstones. The 23.1 carats ( 4.62 g ) Burmese ruby, set in a platinum ring with diamonds, was donated by businessman and philanthropist Peter Buck in memory of his late wife Carmen Lúcia. This 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 Mogok region of Burma ( now Myanmar ) in the 1930s. In 2007 the London jeweler Garrard & Co featured on their website a heart - shaped 40.63 - carat ruby. On December 13 / 14, 2011 Elizabeth Taylor 's complete jewellery collection was auctioned by Christie 's. Several ruby - set pieces were included in the sale, notably a ring set with an 8.24 ct gem that broke the ' price - per - carat ' record for rubies ( $512,925 per carat, i.e. over $4.2 million in total ), and a necklace that sold for over $3.7 million. The Liberty Bell Ruby is the largest mined ruby in the world. It was stolen in a heist in 2011. The Sunrise Ruby is the world 's most expensive ruby, most expensive coloured gemstone, and most expensive gemstone other than a diamond. In May 2015, it sold at auction in Switzerland to an anonymous buyer for US $30 million. A synthetic ruby crystal became the gain medium in the world 's first optical laser, conceived, designed and constructed by Theodore H. `` Ted '' Maiman, on the 16th of May, 1961 at Hughes Research Laboratories. The concept of electromagnetic radiation amplification through the mechanism of Stimulated Emission had already been successfully demonstrated in the laboratory by way of the Maser, using other materials such as ammonia and indeed, later, ruby, but the Ruby Laser was the first device to work at optical ( 694.3 nm ) wavelengths. Maiman 's prototype laser is still in working order. Historical and cultural references In Job 28 : 18 and Proverbs 3 : 15, wisdom is more valuable than rubies. In Proverbs 31 : 10, a wife of noble character is worth more than rubies. An early recorded transport and trading of rubies arises in the literature on the North Silk Road of China, wherein about 200 BC rubies were carried along this ancient trackway moving westward from China. 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. See also Book : Gemstones Gemology and Jewelry portal Anyolite Gemology List of gemstones List of minerals Verneuil process References Jump up ^ Corundum data on Webmineral Jump up ^ Ruby on Gemdat.org Jump up ^ Precious Stones, Max Bauer, p. 2 ^ Jump up to : `` Ruby : causes of color ''. Retrieved 28 Mar 2016. ^ Jump up to : Matlins, Antoinette Leonard ( 2010 ). Colored Gemstones. Gemstone Press. p. 203. ISBN 0 - 943763 - 72 - X. Jump up ^ Reed, Peter ( 1991 ). Gemmology. Butterworth - Heinemann. p. 337. ISBN 0 - 7506 - 6449 - 5. Jump up ^ Wise, Richard G. `` Gemstone Connoisseurship ; The Finer Points, Part II ''. Jump up ^ Hughes, Richard W. `` Walking the line in ruby & sapphire ''. ruby-sapphire.com. Jump up ^ Federman, David. `` Pink Sapphire ''. Modern Jeweler. Jump up ^ http://www.gemsociety.org/article/ruby-sapphire-identifying-origin-understanding-value-rarity-gem-corundum/ Jump up ^ `` This is the New Coat of Arms of Republic of Macedonia - Independent.mk ''. Independent.mk. Retrieved 30 March 2017. Jump up ^ Wenk, Hans - Rudolf ; Bulakh, A.G. ( 2004 ). Minerals : their constitution and origin. Cambridge, U.K. : Cambridge University Press. pp. 539 -- 541. ISBN 0 - 521 - 52958 - 1. ^ Jump up to : Wise, Richard W. ( 2006 ). Secrets Of The Gem Trade, The Connoisseur 's Guide To Precious Gemstones. Brunswick House Press. pp. 18 -- 22. ISBN 0 - 9728223 - 8 - 0. Jump up ^ The Heat Treatment of Ruby and Sapphire. Bangkok, Thailand : Gemlab Inc. 1992. ISBN 0940965100. Jump up ^ Vincent Pardieu Lead Glass Filled / Repaired Rubies. Asian Institute of Gemological Sciences Gem Testing Laboratory. February 2005 Jump up ^ Richard W. Hughes ( 1997 ), Ruby & Sapphire, Boulder, CO, RWH Publishing, ISBN 978 - 0 - 9645097 - 6 - 4 Jump up ^ Milisenda, CC ( 2005 ). `` Rubine mit bleihaltigen Glasern gefullt ''. Zeitschrift der Deutschen Gemmologischen Gesellschaft ( in German ). Deutschen Gemmologischen Gesellschaft. 54 ( 1 ) : 35 -- 41. Jump up ^ `` Lead Glass - Filled Rubies ''. GIA Global Dispatch. Gemological Institute of America. 2012. Jump up ^ `` Bahadur : a Handbook of Precious Stones ''. 1943. Retrieved 2007 - 08 - 19. ^ Jump up to : Maiman, T.H. ( 1960 ). `` Stimulated optical radiation in ruby ''. Nature. 187 ( 4736 ) : 493 -- 494. Bibcode : 1960Natur. 187... 493M. doi : 10.1038 / 187493a0. Jump up ^ `` Thomas Nicols : A Lapidary or History of Gemstones ''. 1652. Retrieved 2007 - 08 - 19. Jump up ^ `` The Carmen Lúcia Ruby ''. Exhibitions. Retrieved 2008 - 02 - 28. Jump up ^ `` Garrards -- Treasures ( large and important jewelry pieces ) ''. Retrieved 2010 - 11 - 08. Jump up ^ The Legendary Jewels, Evening Sale & Jewelry ( Sessions II and III ) Press Release Christie 's. Christies.com ( 2011 - 12 - 14 ). Retrieved on 2012 - 07 - 11. Jump up ^ Elizabeth Taylor 's ruby and diamond necklace. News.yahoo.com ( 2011 - 09 - 07 ). Retrieved on 2012 - 07 - 11. Jump up ^ http://philadelphia.cbslocal.com/2012/01/09/irreplaceable-2-million-ruby-stolen-in-wilmington-jewelry-heist/ Jump up ^ `` World 's most expensive coloured gem sells for $30 m ''. BBC. 13 May 2015. Retrieved 13 May 2015. Jump up ^ `` Laser inventor Maiman dies ; tribute to be held on anniversary of first laser ''. Laser Focus World. 2007 - 05 - 09. Retrieved 2007 - 05 - 14. Jump up ^ C. Michael Hogan, Silk Road, North China, The Megalithic Portal. 19 November 2007 Jump up ^ Smith, Henry G. ( 1896 ). `` Chapter 2, Sapphires, Rubies ''. Gems and Precious Stones. Charles Potter Government Printer, Australia. External links Wikimedia Commons has media related to Ruby. International Colored Stone Association 's ruby overview page Webmineral crystallographic and mineral info Jewellery Forms Anklet Barrette Belt buckle Belly chain Bindi Bracelet Brooch Chatelaine Collar pin Crown Cufflink Earring Ferronnière Lapel pin Necklace Pectoral Pendant Ring Tiara Tie clip Tie pin Toe ring Watch pocket strap Making People Bench jeweler Clockmaker Goldsmith Silversmith Jewelry designer Lapidary Watchmaker Processes Carving Casting centrifugal lost - wax vacuum Enameling Engraving Filigree Kazaziye Metal clay Plating Polishing Repoussé and chasing Soldering Stonesetting Wire sculpture Wire wrapped jewelry Tools Draw plate File Hammer Mandrel Pliers Materials Precious metals Gold Palladium Platinum Rhodium Silver Precious metal alloys Britannia silver Colored gold Crown gold Electrum Shakudō Shibuichi Sterling silver Tumbaga Base metals Brass Bronze Copper Mokume - gane Pewter Stainless steel Titanium Tungsten Mineral gemstones Aventurine Agate Amethyst Beryl Carnelian Chrysoberyl Diamond Diopside Emerald Garnet Jade Jasper Lapis lazuli Larimar Malachite Marcasite Moonstone Obsidian Onyx Opal Pearl Peridot Prasiolite Quartz Ruby Sapphire Sodalite Spinel Sunstone Tanzanite Tiger 's eye Topaz Tourmaline Turquoise Zircon Organic gemstones Abalone Amber Ammolite Copal Coral Ivory Jet Nacre Other natural objects Bog - wood Hair Shell jewelry Toadstone Terms Carat ( mass ) Carat ( purity ) Finding Millesimal fineness Art jewelry Related topics Body piercing Fashion Gemology Phaleristics Metalworking Wearable art Gemstones Gemmological Classifiactions by E. Ya. Kievlenko, 1980, updated Jewelry stones 1st order Diamond Ruby Emerald Blue Sapphire Alexandrite Natural marine pearls 2nd order Pink sapphire Demantoid Tsavorite Spinel Precious Black Opal Tanzanite 3rd order Yellow, Green, Violet Sapphires Aquamarine Orange topaz ( Imperial ) Rubellite Precious White and Fire Opal 4th order Tourmaline -- Verdelite Indicolite, polychromous Beryl -- Heliodor, pink, yellow - green Topaz yellow, blue, pink Peridot Garnets -- Spessartine ( malaya ), Rhodolite, Almandine, Pyrope Amethyst Citrine Blue Turquoise Jewelry - Industrial stones 1st order Lazurite Jadeite Nephrite Malachite Amber ( Baltic amber ) Chrysoprase Charoite 2nd order Agate Amazonite Rhodonite Colorless, smoky and pink quartz Hematite Common opal Opaque iridescent feldspars Industrial stones Jasper Graphic granite Petrified wood Cacholong ( Porouse opal ) Marble onyx Obsidian Listwanite ( green mica ) Jet Selenite Fluorite Serpentinite Aventurine quartzite Ophicalcite ( Serpentine / Calcite ) Pagodite ( Pyrophyllite / Talc ) Retrieved from `` https://en.wikipedia.org/w/index.php?title=Ruby&oldid=800440177 '' Categories : Aluminium minerals Oxide minerals Superhard materials Trigonal minerals Luminescent minerals Corundum gemstones Hidden categories : CS1 German - language sources ( de ) Wikipedia semi-protected pages All articles with unsourced statements Articles with unsourced statements from November 2012 Pages with numeric Bible version references Use American English from August 2015 All Wikipedia articles written in American English Use mdy dates from August 2015 Talk View source Contents About Wikipedia Tools Wikiquote Aragonés Asturianu Azərbaycanca تۆرکجه Bahasa Banjar Bân - lâm - gú Беларуская Беларуская ( тарашкевіца ) ‎ Български Català Čeština Cymraeg Dansk Deutsch Eesti Ελληνικά Español Esperanto Euskara فارسی Français Gaeilge Galego गोंयची कोंकणी / Gõychi Konknni 客家 語 / Hak - kâ - ngî 한국어 Հայերեն हिन्दी Hrvatski Ido Bahasa Indonesia Interlingua Italiano עברית ಕನ್ನಡ ქართული Kaszëbsczi Қазақша Latina Latviešu Lëtzebuergesch Lietuvių മലയാളം मराठी مصرى Bahasa Melayu မြန်မာဘာသာ Nederlands नेपाल भाषा 日本 語 Norsk Norsk nynorsk Oʻzbekcha / ўзбекча ਪੰਜਾਬੀ پنجابی پښتو Polski Português Română Runa Simi Русский संस्कृतम् Scots සිංහල Simple English Slovenčina Slovenščina کوردی Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska தமிழ் తెలుగు ไทย Тоҷикӣ Türkçe Українська اردو ئۇيغۇرچە / Uyghurche Tiếng Việt ייִדיש 粵語 中文 Kabɩyɛ Edit links This page was last edited on 13 September 2017, at 15 : 25. 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Question: where can rubies be found in the us
Answer: Montana