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Ruby is a pinkish red to blood-red colored
gemstone A gemstone (also called a fine gem, jewel, precious stone, or semiprecious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli, opal, ...
, a variety of the
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...
corundum Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the pres ...
( aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called
sapphire Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide () with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium. The name sapphire is derived via the Latin "sapphir ...
s. Ruby is one of the traditional
cardinal gem Cardinal gems are gemstones which have traditionally been considered precious above all others. The classification of the cardinal gems dates back to antiquity, and was largely determined by ceremonial or religious use and rarity. The term has larg ...
s, alongside
amethyst Amethyst is a violet variety of quartz. The name comes from the Koine Greek αμέθυστος ''amethystos'' from α- ''a-'', "not" and μεθύσκω (Ancient Greek) / μεθώ (Modern Greek), "intoxicate", a reference to the belief that t ...
,
sapphire Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide () with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium. The name sapphire is derived via the Latin "sapphir ...
,
emerald Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium or sometimes vanadium.Hurlbut, Cornelius S. Jr. and Kammerling, Robert C. (1991) ''Gemology'', John Wiley & Sons, New York, p ...
, and
diamond Diamond is a Allotropes of carbon, solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the Chemical stability, chemically stable form of car ...
. The word ''ruby'' comes from ''ruber'',
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
for red. The color of a ruby is due to the element
chromium Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal. Chromium metal is valued for its high corrosion resistance and hardne ...
. Some gemstones that are popularly or historically called rubies, such as the
Black Prince's Ruby The Black Prince's Ruby is a large, irregular cabochon red spinel weighing set in the cross pattée above the Cullinan II diamond at the front of the Imperial State Crown of the United Kingdom. The spinel is one of the oldest parts of the Crown ...
in the British
Imperial State Crown The Imperial State Crown is one of the Crown Jewels of the United Kingdom and symbolises the sovereignty of the monarch. It has existed in various forms since the 15th century. The current version was made in 1937 and is worn by the monarc ...
, are actually
spinel Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , which means ''spine'' in reference to its pointed crystals. Properties S ...
s. These were once known as "Balas rubies". 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 Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer Polymorphism (materials science), polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest ...
inclusions may indicate that the stone has been treated. Ruby is the traditional
birthstone A birthstone is a gemstone A gemstone (also called a fine gem, jewel, precious stone, or semiprecious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rock ...
for July and is usually
pink Pink is the color of a namesake flower that is a pale tint of red. It was first used as a color name in the late 17th century. According to surveys in Europe and the United States, pink is the color most often associated with charm, politeness, ...
er than
garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different s ...
, although some
rhodolite Rhodolite is a varietal name for rose-pink to red mineral pyrope, a species in the garnet group. It was first described from Cowee Valley, Macon County, North Carolina. The name is derived from the Greek "rhodon" for "rose-like", in common wit ...
garnets have a similar pinkish hue to most rubies. The world's most valuable ruby to be sold at auction is the
Sunrise Ruby The Sunrise Ruby is the world's most expensive ruby, most expensive coloured gemstone, and most expensive gemstone other than a diamond. Originally mined in Myanmar, its current name is derived from a poem of the same name, written by the 13t ...
, which sold for US$34.8 million.


Physical properties

Rubies have a
hardness In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...
of 9.0 on the
Mohs scale of mineral hardness The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by th ...
. Among the natural gems, only
moissanite Moissanite () is naturally occurring silicon carbide and its various crystalline polymorphs. It has the chemical formula SiC and is a rare mineral, discovered by the French chemist Henri Moissan in 1893. Silicon carbide is useful for commercial ...
and
diamond Diamond is a Allotropes of carbon, solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the Chemical stability, chemically stable form of car ...
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 AlO, in which 3 electrons leave each aluminium
ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
to join the regular octahedral group of six nearby O ions; in pure corundum this leaves all of the aluminium ions with a very stable configuration of no unpaired electrons or unfilled energy levels, and the crystal is perfectly colorless, and transparent except for flaws. When a chromium atom replaces an occasional aluminium atom, it too loses 3 electrons to become a chromium ion to maintain the charge balance of the AlO crystal. However, the Cr ions are larger and have
electron orbitals An electron orbital may refer to: * An atomic orbital, describing the behaviour of an electron in an atom * A molecular orbital, describing the behaviour of an electron in a molecule See also * Electron configuration, the arrangement of electr ...
in different directions than aluminium. 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. If one percent of the aluminium 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 Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...
emission of 694-nanometer-wavelength red light, which adds to its red color and perceived luster. The chromium concentration in artificial rubies can be adjusted (in the crystal growth process) to be ten to twenty times less than in the natural gemstones.
Theodore Maiman Theodore Harold Maiman (July 11, 1927 – May 5, 2007) was an American engineer and physicist who is widely credited with the invention of the laser.Johnson, John Jr. (May 11, 2008). "Theodore H. Maiman, at age 32; scientist created the first LA ...
says that "because of the low chromium level in these crystals they display a lighter red color than gemstone ruby and are referred to as pink ruby." After absorbing short-wavelength light, there is a 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 A ruby laser is a solid-state laser that uses a synthetic ruby crystal as its gain medium. The first working laser was a ruby laser made by Theodore H. "Ted" Maiman at Hughes Research Laboratories on May 16, 1960. Ruby lasers produce pulses of c ...
in this way produces a very high intensity of
coherent Coherence, coherency, or coherent may refer to the following: Physics * Coherence (physics), an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference * Coherence (units of measurement), a deri ...
red light. All natural rubies have imperfections in them, including color impurities and inclusions of
rutile Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer Polymorphism (materials science), polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest ...
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 A cabochon (; ) is a gemstone that has been shaped and polished, as opposed to faceted. The resulting form is usually a convex (rounded) obverse with a flat reverse. Cabochon was the default method of preparing gemstones before gemstone cuttin ...
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 Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer Polymorphism (materials science), polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest ...
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 In gemology, chatoyancy ( ), or chatoyance or cat's eye effect, is an optical reflectance effect seen in certain gemstones, woods, and carbon fibre. Coined from the French "œil de chat", meaning "cat's eye", chatoyancy arises either from the ...
or the "cat's eye" effect.


Versus 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 Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide () with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium. The name sapphire is derived via the Latin "sa ...
. 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.


Occurrence and mining

Historically, rubies have been mined in Thailand, in the
Pailin Pailin ( km, ប៉ៃលិន, ) is a province in western Cambodia at the northern edge of the Cardamom Mountains near the border of Thailand. This province is surrounded by Battambang province, and was officially carved out of Battambang ...
and
Samlout District Samlout ( km, សំឡូត ) or Samlot is a district (''srok'') of Battambang Province, in northwestern Cambodia. Administration The district is subdivided into 7 communes (''khum'') and 49 villages (''phum Administrative divisions o ...
of
Cambodia Cambodia (; also Kampuchea ; km, កម្ពុជា, UNGEGN: ), officially the Kingdom of Cambodia, is a country located in the southern portion of the Indochinese Peninsula in Southeast Asia, spanning an area of , bordered by Thailand t ...
, as well as in
Afghanistan Afghanistan, officially the Islamic Emirate of Afghanistan,; prs, امارت اسلامی افغانستان is a landlocked country located at the crossroads of Central Asia and South Asia. Referred to as the Heart of Asia, it is bordere ...
,
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
,
Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
,
Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...
,
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
,
Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...
,
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
, and Scotland. After the
Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
, ruby deposits were found in
Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
,
Mozambique Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi ...
, Nepal, Pakistan,
Tajikistan Tajikistan (, ; tg, Тоҷикистон, Tojikiston; russian: Таджикистан, Tadzhikistan), officially the Republic of Tajikistan ( tg, Ҷумҳурии Тоҷикистон, Jumhurii Tojikiston), is a landlocked country in Centr ...
,
Tanzania Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands and ...
, and
Vietnam Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...
. The
Republic of North Macedonia North Macedonia, ; sq, Maqedonia e Veriut, (Macedonia before February 2019), officially the Republic of North Macedonia,, is a country in Southeast Europe. It gained independence in 1991 as one of the successor states of Yugoslavia. It ...
is the only country in mainland Europe to have naturally occurring rubies. They can mainly be found around the city of
Prilep Prilep ( mk, Прилеп ) is the fourth-largest city in North Macedonia. It has a population of 66,246 and is known as "the city under Marko's Towers" because of its proximity to the towers of Prince Marko. Name The name of Prilep appear ...
. Macedonian rubies have a unique raspberry color. A few rubies have been found in the U.S. states of
Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...
,
North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and So ...
,
South Carolina )''Animis opibusque parati'' ( for, , Latin, Prepared in mind and resources, links=no) , anthem = " Carolina";" South Carolina On My Mind" , Former = Province of South Carolina , seat = Columbia , LargestCity = Charleston , LargestMetro = ...
and
Wyoming Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the south ...
.
Spinel Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , which means ''spine'' in reference to its pointed crystals. Properties S ...
, another red gemstone, is sometimes found along with rubies in the same gem gravel or marble. Red spinels may be mistaken for rubies by those lacking experience with gems. However, the finest red spinels, now heavily sought, can have values approaching all but the finest examples of ruby. The
Mogok Mogok (, ; Shan: , ) is a town in the Thabeikkyin District of Mandalay Region of Myanmar, located north of Mandalay and north-east of Shwebo. History Mogok is believed to have been founded in 1217 by three lost Shan hunters who discovered r ...
Valley in
Upper Myanmar Upper Myanmar ( my, အထက်မြန်မာပြည်, also called Upper Burma) is a geographic region of Myanmar, traditionally encompassing Mandalay and its periphery (modern Mandalay, Sagaing, Magway Regions), or more broadly speak ...
(Burma) was for centuries the world's main source for rubies. That region has produced some exceptional rubies; however, in recent years few good rubies have been found. 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. In Pakistani Kashmir there are vast proven reserves of millions of rubies, worth up to half a billion dollars. However, as of 2017 there was only one mine (at Chitta Katha) due to lack of investment. In
Afghanistan Afghanistan, officially the Islamic Emirate of Afghanistan,; prs, امارت اسلامی افغانستان is a landlocked country located at the crossroads of Central Asia and South Asia. Referred to as the Heart of Asia, it is bordere ...
, rubies are mined at Jegdalek. In 2017 the Aappaluttoq mine in Greenland began running. The rubies in Greenland are said to be among the oldest in the world at approximately 3 billion years old. The Aappaluttoq mine in Greenland is located 160 kilometers south of Nuuk, the capital of Greenland. The rubies are traceable from mine to market. The Montepuez ruby mine in northeastern Mozambique is situated on one of the most significant ruby deposits in the world, although, rubies were only discovered here for the first time in 2009. In less than a decade, Mozambique has become the world's most productive source for gem-quality 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. Image:Ruby cristal.jpg, A naturally occurring ruby crystal Image:Ruby gem.JPG, Natural ruby with inclusions Image:Cut Ruby.jpg, A cut pink ruby Image:Rubis, calcite 14.jpg, Purple rubies


Clarity

Because rubies host many inclusions, their clarity is evaluated by the inclusions’ size, number, location, and visibility. Rubies with the highest clarity grades are known as “eye-clean,” because their inclusions are the least visible to the naked human eye. Rubies may also have thin, intersecting inclusions called silk. Silk can scatter light, brightening the gem's appearance, and the presence of silk can also show whether a ruby has been previously heat treated, since intense heat will degrade a ruby's silk.


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 Lead glass, commonly called crystal, is a variety of glass in which lead replaces the calcium content of a typical potash glass. Lead glass contains typically 18–40% (by weight) lead(II) oxide (PbO), while modern lead crystal, historically als ...
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 Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock i ...
# 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 be identified by noting bubbles in cavities and fractures using a 10× loupe.


Synthesis and imitation

In 1837, Gaudin made the first synthetic rubies by fusing
potash alum Potassium alum, potash alum, or potassium aluminium sulfate is a chemical compound: the double sulfate of potassium and aluminium, with chemical formula KAl(SO4)2. It is commonly encountered as the dodecahydrate, KAl(SO4)2·12H2O. It crystalli ...
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,
Edmond Frémy Edmond Frémy (; 28 February 1814 – 3 February 1894) was a French chemist. He is perhaps best known today for Frémy's salt, a strong oxidizing agent which he discovered in 1845. Fremy's salt is a long-lived free radical that finds use as a s ...
and industrial glass-maker Charles Feil made crystal
corundum Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the pres ...
from which small stones could be cut. In 1887, Fremy and Auguste Verneuil manufactured artificial ruby by fusing BaF and AlO with a little chromium at
red heat The practice of using colours to determine the temperature of a piece of (usually) ferrous metal comes from blacksmithing. Long before thermometers were widely available it was necessary to know what state the metal was in for heat treating it an ...
. In 1903, Verneuil announced he could produce synthetic rubies on a commercial scale using this flame fusion process, later also known as the
Verneuil process The Verneuil method (or Verneuil process or Verneuil technique), also called flame fusion, was the first commercially successful method of manufacturing synthetic gemstones, developed in the late 1883 by the French chemist Auguste Verneuil. It ...
. By 1910, Verneuil's laboratory had expanded into a 30 furnace production facility, with annual gemstone production having reached 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 curved
striae Stretch marks, also known as striae () or striae distensae, are a form of scarring on the skin with an off-color hue. Over time they may diminish, but will not disappear completely. Striae are caused by tearing of the dermis during periods of r ...
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 A dopant, also called a doping agent, is a trace of impurity element that is introduced into a chemical material to alter its original electrical or optical properties. The amount of dopant necessary to cause changes is typically very low. When ...
s are added to some manufactured rubies so they can be identified as synthetic, but most need
gemological Gemology or gemmology is the science dealing with natural and artificial gemstone materials. It is a geoscience and a branch of mineralogy. Some jewelers (and many non-jewelers) are academically trained gemologists and are qualified to identify ...
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 A ruby laser is a solid-state laser that uses a synthetic ruby crystal as its gain medium. The first working laser was a ruby laser made by Theodore H. "Ted" Maiman at Hughes Research Laboratories on May 16, 1960. Ruby lasers produce pulses of c ...
s and
maser A maser (, an acronym for microwave amplification by stimulated emission of radiation) is a device that produces coherent electromagnetic waves through amplification by stimulated emission. The first maser was built by Charles H. Townes, Ja ...
s. The first working laser was made by
Theodore H. Maiman Theodore Harold Maiman (July 11, 1927 – May 5, 2007) was an American engineer and physicist who is widely credited with the invention of the laser.Johnson, John Jr. (May 11, 2008). "Theodore H. Maiman, at age 32; scientist created the first LA ...
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 mechanical clockworks, or as scanning probe tips in a
coordinate measuring machine A coordinate measuring machine (CMM) is a device that measures the geometry of physical objects by sensing discrete points on the surface of the object with a probe. Various types of probes are used in CMMs, the most common being mechanical and l ...
. Imitation rubies are also marketed. Red
spinel Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , which means ''spine'' in reference to its pointed crystals. Properties S ...
s, red
garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different s ...
s, 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 Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , which means ''spine'' in reference to its pointed crystals. Properties Sp ...
for red spinel and
rubellite Rubellite is the red or pink variety of tourmaline and is a member of elbaite. Rubellite is also the rarest gem in its gem family. It is occasionally mistaken for ruby. These gems typically contain inclusions. Notable places where rubellite ca ...
for red
tourmaline Tourmaline ( ) is a crystalline silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is a gemstone and can be found in a wide variety of colors. The ...
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 examples

* The Smithsonian's
National Museum of Natural History The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. In 2021, with 7 ...
in Washington, D.C. has some of the world's largest and finest ruby gemstones. The Burmese ruby, set in a platinum ring with diamonds, was donated by businessman and philanthropist
Peter Buck Peter Lawrence Buck (born December 6, 1956) is an American musician and songwriter. He was a co-founder and the lead guitarist of the alternative rock band R.E.M. He also plays the banjo and mandolin on several R.E.M. songs. Throughout his car ...
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 Mogok (, ; Shan: , ) is a town in the Thabeikkyin District of Mandalay Region of Myanmar, located north of Mandalay and north-east of Shwebo. History Mogok is believed to have been founded in 1217 by three lost Shan hunters who discovered r ...
region of
Burma Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...
(now
Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John C. Wells, Joh ...
) in the 1930s. * In 2007, the London jeweler
Garrard & Co Garrard & Co. Limited, formerly Asprey & Garrard Limited, designs and manufactures luxury jewellery and silver. George Wickes founded Garrard in London in 1735 and the brand is headquartered at Albemarle Street in Mayfair, London. Garrard also h ...
featured a heart-shaped 40.63-carat ruby on their website. * On 13/14 December 2011,
Elizabeth Taylor Dame Elizabeth Rosemond Taylor (February 27, 1932 – March 23, 2011) was a British-American actress. She began her career as a child actress in the early 1940s and was one of the most popular stars of classical Hollywood cinema in the 1950s. ...
's complete jewelry collection was auctioned by
Christie's Christie's is a British auction house founded in 1766 by James Christie (auctioneer), James Christie. Its main premises are on King Street, St James's in London, at Rockefeller Center in New York City and at Alexandra House in Hong Kong. It is ...
. 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 (
US$ The United States dollar (symbol: $; code: USD; also abbreviated US$ or U.S. Dollar, to distinguish it from other dollar-denominated currencies; referred to as the dollar, U.S. dollar, American dollar, or colloquially buck) is the official ...
512,925 per carat – i.e., over US$4.2 million in total), and a necklace that sold for over US$3.7 million. * The
Liberty Bell Ruby The Liberty Bell Ruby is a sculpture crafted from the world's largest mined ruby, discovered in East Africa in the 1950s. It weighs four pounds, is eight and a half thousand carats, and is sculpted into a miniature form of the Liberty Bell. It has ...
is the largest mined ruby in the world. It was stolen in a heist in 2011. * The
Sunrise Ruby The Sunrise Ruby is the world's most expensive ruby, most expensive coloured gemstone, and most expensive gemstone other than a diamond. Originally mined in Myanmar, its current name is derived from a poem of the same name, written by the 13t ...
is the world's most expensive ruby, most expensive colored 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 16 May 1961 at Hughes Research Laboratories The concept of electromagnetic radiation amplification through the mechanism of
stimulated emission Stimulated emission is the process by which an incoming photon of a specific frequency can interact with an excited atomic electron (or other excited molecular state), causing it to drop to a lower energy level. The liberated energy transfers to th ...
had already been successfully demonstrated in the laboratory by way of the
maser A maser (, an acronym for microwave amplification by stimulated emission of radiation) is a device that produces coherent electromagnetic waves through amplification by stimulated emission. The first maser was built by Charles H. Townes, Ja ...
, using other materials such as ammonia and, later, ruby, but the
ruby laser A ruby laser is a solid-state laser that uses a synthetic ruby crystal as its gain medium. The first working laser was a ruby laser made by Theodore H. "Ted" Maiman at Hughes Research Laboratories on May 16, 1960. Ruby lasers produce pulses of c ...
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

* The
Old Testament The Old Testament (often abbreviated OT) is the first division of the Christian biblical canon, which is based primarily upon the 24 books of the Hebrew Bible or Tanakh, a collection of ancient religious Hebrew writings by the Israelites. The ...
of the
Bible The Bible (from Koine Greek , , 'the books') is a collection of religious texts or scriptures that are held to be sacred in Christianity, Judaism, Samaritanism, and many other religions. The Bible is an anthologya compilation of texts of a ...
mentions ruby many times in the
Book of Exodus The Book of Exodus (from grc, Ἔξοδος, translit=Éxodos; he, שְׁמוֹת ''Šəmōṯ'', "Names") is the second book of the Bible. It narrates the story of the Exodus, in which the Israelites leave slavery in Biblical Egypt through t ...
, and many times in the
Book of Proverbs The Book of Proverbs ( he, מִשְלֵי, , "Proverbs (of Solomon)") is a book in the third section (called Ketuvim) of the Hebrew Bible and a book of the Christian Old Testament. When translated into Greek and Latin, the title took on different ...
, as well as various other times. It is not certain that the Biblical words mean 'ruby' as distinct from other jewels. * An early recorded transport and trading of rubies arises in the literature on the
North Silk Road The Northern Silk Road is an ancient trackway in northern China originating in the early capital of Xi'an and extending north of the Taklamakan Desert to reach the ancient kingdoms of Parthia, Bactria and eventually Persia and Rome. It is the no ...
of China, wherein about 200 BC rubies were carried along this ancient
trackway Historic roads (historic trails in USA and Canada) are paths or routes that have historical importance due to their use over a period of time. Examples exist from prehistoric times until the early 20th century. They include ancient trackway ...
moving westward from China.C. Michael Hogan
Silk Road, North China
, The Megalithic Portal. 19 November 2007
* 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. * A traditional
Hindu Hindus (; ) are people who religiously adhere to Hinduism.Jeffery D. Long (2007), A Vision for Hinduism, IB Tauris, , pages 35–37 Historically, the term has also been used as a geographical, cultural, and later religious identifier for ...
astrological belief holds rubies as the "gemstone of the
Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
and also the heavenly deity
Surya Surya (; sa, सूर्य, ) is the sun as well as the solar deity in Hinduism. He is traditionally one of the major five deities in the Smarta tradition, all of whom are considered as equivalent deities in the Panchayatana puja and a m ...
, the leader of the nine heavenly bodies (
Navagraha Navagraha are nine heavenly bodies and deities that influence human life on Earth according to Hinduism and Hindu astrology. The term is derived from ''nava'' ( sa, नव "nine") and ''graha'' ( sa, ग्रह "planet, seizing, laying hold of, ...
)." The belief is that worshiping and wearing rubies causes the Sun to be favorable to the wearer. * In the Marvel comic books, the Godstone is a ruby that the son of J. Jonah Jameson, John Jameson found on the Moon that becomes activated by moonlight, grafts itself to his chest which turns him into the Man-Wolf.


See also

*
Anyolite Anyolite is a metamorphic rock composed of intergrown green zoisite, black/dark green pargasite and ruby. It has been found in the Arusha Region of Tanzania and in Austria. It is sometimes incorrectly advertised as a variety of the mineral zoisit ...
*
List of individual gemstones A number of gemstones have gained fame, either because of their size and beauty or because of the people who owned or wore them. A list of famous gemstones follows. Alexandrites * Smithsonian museums' Alexandrite, the largest cut alexandrite ...
*
List of minerals This is a list of minerals for which there are articles on Wikipedia. Minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various ''species''. Within a m ...
*
Shelby Gem Factory The Shelby Gem Factory was the production facility of ICT Incorporated, a company in Shelby, Michigan, United States, that manufactured artificial gemstones through proprietary processes. ICT began operations in 1970 and closed in December 201 ...
*
Verneuil process The Verneuil method (or Verneuil process or Verneuil technique), also called flame fusion, was the first commercially successful method of manufacturing synthetic gemstones, developed in the late 1883 by the French chemist Auguste Verneuil. It ...
*
Emerald Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium or sometimes vanadium.Hurlbut, Cornelius S. Jr. and Kammerling, Robert C. (1991) ''Gemology'', John Wiley & Sons, New York, p ...


References


External links


International Colored Stone Association's ruby overview page

Webmineral crystallographic and mineral info
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