Amethyst

Amethyst is a violet array of quartz. The name comes from the Koine Greek αμέθυστος amethystos from α- a-, "not" and μεθύσκω (Ancient Greek) methysko / μεθώ metho (Modern Greek), "intoxicate", a advertence to the acceptance that the bean able its buyer from drunkenness.[1] The age-old Greeks wore amethyst and carved bubbler argosy from it in the acceptance that it would anticipate intoxication.

Amethyst is a semiprecious bean that is about acclimated in adornment and is the acceptable birthstone for February.

Structure

Faceted amethyst

Emerald cut amethyst

Amethyst crystals from Mexico

Amethyst crystals from Mexico

Amethyst is a amethyst array of quartz (SiO2) and owes its violet blush to irradiation, algae of adamant and in some cases added alteration metals, and the attendance of added trace elements, which aftereffect in circuitous bright filigree substitutions.[2][3][4] The acerbity of the mineral is the aforementioned as quartz, appropriately authoritative it acceptable for use in jewelry.

Hue and tone

Amethyst occurs in primary hues from a ablaze pinkish violet blush to a abysmal amethyst color. Amethyst may affectation one or both accessory hues, red and blue.[5] High affection amethyst can be begin in Siberia, Sri Lanka, Brazil, Uruguay, and the far East. The ideal brand is alleged "Deep Siberian" and has a primary amethyst hue of about 75–80%, with 15–20% dejected and (depending on the ablaze source) red accessory hues.[6] ‘Rose de France’ is authentic by its clearly ablaze adumbration of the purple, evocative of a lavender/lilac shade. These anemic colors were already advised abominable but accept afresh become accepted due to accelerated marketing.

Green quartz is sometimes afield alleged blooming amethyst, which is a misnomer and not an adapted name for the material, the able analogue actuality prasiolite. Added names for blooming quartz are vermarine or adhesive citrine.

Of actual capricious intensity, the blush of amethyst is about laid out in stripes alongside to the final faces of the crystal. One aspect in the art of lapidary involves accurately acid the bean to abode the blush in a way that makes the accent of the accomplished gem homogeneous. Often, the actuality that sometimes alone a attenuate apparent band of violet blush is present in the bean or that the blush is not constant makes for a difficult cutting. It can alike cut bright quartz, which is one of Earth’s sharpest gems.

The blush of amethyst has been approved to aftereffect from barter by betterment of trivalent adamant (Fe3+) for silicon in the structure,[4][7] in the attendance of trace elements of ample ionic radius,[3] and, to a assertive extent, the amethyst blush can artlessly aftereffect from displacement of alteration elements alike if the adamant absorption is low. Accustomed amethyst is dichroic in brownish violet and bluish violet,[4] but back heated, turns yellow-orange, yellow-brown, or aphotic brownish and may resemble citrine,[8] but loses its dichroism, clashing 18-carat citrine. Back partially heated, amethyst can aftereffect in ametrine.

Amethyst can achromatize in accent if overexposed to ablaze sources and can be artificially blurred with able irradiation.[4] It does not fluoresce beneath either short-wave or long-wave UV light.

Geographic distribution

An amethyst geode that formed back ample crystals grew in accessible spaces central the rock.

Amethyst is produced in affluence from the accompaniment of Rio Grande do Sul in Brazil area it occurs in ample geodes aural agitable rocks. [9][10][11][12][13]Many of the alveolate agates of southwestern Brazil and Uruguay accommodate a crop of amethyst crystals in the interior. Artigas, Uruguay and adjoining Brazilian accompaniment Rio Grande do Sul are ample apple producers beyond in abundance Minas Gerais, as able-bodied as Mato Grosso, Espirito Santo, Bahia, and Ceará states, all amethyst producers of accent in Brazil.

Amethyst from Brazil in the Mineral building in India

It is additionally begin and mined in South Korea. The better opencast amethyst attitude in the apple is in Maissau, Lower Austria. Much accomplished amethyst comes from Russia, abnormally from abreast Mursinka in the Ekaterinburg district, area it occurs in drusy cavities in granitic rocks. Abounding localities in south India crop amethyst.[1] One of the better all-around amethyst producers is Zambia in southern Africa with an anniversary assembly of about 1000 tons.

Amethyst occurs at abounding localities in the United States. Among these may be mentioned: the Mazatzal Mountain arena in Gila and Maricopa Counties, Arizona; Red Feather Lakes, abreast Fort Collins, Colorado; Amethyst Mountain, Texas; Yellowstone National Park; Delaware County, Pennsylvania; Haywood County, North Carolina; Deer Hill and Stow, Maine and in the Lake Superior arena of Minnesota, Wisconsin and Michigan.[1] Amethyst is almost accepted in the Canadian ambit of Ontario and Nova Scotia. The better amethyst abundance in North America is amid in Thunder Bay, Ontario.

Amethyst is the official accompaniment gemstone of South Carolina. Several South Carolina amethysts are on affectation at the Smithsonian Building of Accustomed History.[14]

History

Roman bite engraved gem of Caracalla in amethyst, already in the Treasury of Sainte-Chapelle.

Uninscribed amethyst scarab at the centermost of a cord of amethyst brawl beads. Middle Kingdom. From Egypt. The Petrie Building of Egyptian Archaeology, London

Amethyst was acclimated as a gemstone by the age-old Egyptians and was abundantly active in antique for bite engraved gems.[15]

The Greeks believed amethyst gems could anticipate intoxication,[16] while medieval European soldiers wore amethyst amulets as aegis in activity in the acceptance that amethysts alleviate bodies and accumulate them cool-headed.[17] Chaplet of amethyst were begin in Anglo-Saxon graves in England.[18] Anglican bishops abrasion an apostolic arena about set with an amethyst, an allusion to the description of the Apostles as "not drunk" at Pentecost in Acts 2:15.[19]

A ample geode, or "amethyst-grotto", from abreast Santa Cruz in southern Brazil was presented at a 1902 exhibition in Düsseldorf, Germany.[1]

In the 19th century, the blush of amethyst was attributed to the attendance of manganese. However, back it can be abundantly adapted and alike absolved by heat, the blush was believed by some authorities to be from an amoebic source. Adamant thiocyanate has been suggested, and sulfur was said to accept been detected in the mineral.[1]

Synthetic amethyst

Synthetic (laboratory-grown) amethyst is produced by a amalgam adjustment alleged hydrothermal growth, which grows the crystals central a high-pressure autoclave.

Synthetic amethyst is fabricated to imitate the best affection amethyst. Its actinic and concrete backdrop are the aforementioned as that of accustomed amethyst and it can not be differentiated with complete authoritativeness after avant-garde gemmological testing (which is about cost-prohibitive). One analysis based on "Brazil law twinning" (a anatomy of quartz twinning area appropriate and larboard duke quartz structures are accumulated in a distinct crystal[20]) can be acclimated to analyze best constructed amethyst rather easily. It is accessible to amalgamate twinned amethyst, but this blazon is not accessible in ample quantities in the market.[6]

Single-crystal quartz is actual adorable in the industry, decidedly for befitting the approved accordance all-important for quartz movements in watches and clocks, which is area a lot of constructed quartz is used.

Treated amethyst is produced by gamma ray, X-ray or electron axle betterment of bright quartz (rock crystal) which has been aboriginal benumbed with adamant impurities. Exposure to calefaction partially cancels the betterment furnishings and amethyst about becomes chicken or alike green. Much of the citrine, cairngorm, or chicken quartz of adornment is said to be alone "burnt amethyst".[1][21]

Cultural history

Ancient Greece

The Greek chat "amethystos" may be translated as "not drunken", from Greek a-, "not" + methustos, "intoxicated". Amethyst was advised to be a able antitoxin adjoin drunkenness,[22] which is why wine goblets were about carved from it.[23] In his composition "L'Amethyste, ou les Amours de Bacchus et d'Amethyste" (Amethyst or the loves of Bacchus and Amethyste), the French artist Remy Belleau (1528–1577) invented a allegory in which Bacchus, the god of intoxication, of wine, and grapes was advancing a beginning alleged Amethyste, who banned his affections. Amethyste prayed to the gods to abide chaste, a adoration which the austere goddess Diana answered, transforming her into a white stone. Humbled by Amethyste's admiration to abide chaste, Bacchus caked wine over the bean as an offering, dyeing the crystals purple.[24][25]

Variations of the adventure accommodate that Dionysus had been angered by a bitter and swore to annihilate the abutting bitter who beyond his path, creating angry tigers to backpack out his wrath. The bitter angry out to be a admirable adolescent woman, Amethystos, who was on her way to pay accolade to Artemis. Her activity was absolved by Artemis, who adapted the beginning into a bronze of authentic apparent quartz to assure her from the barbarous claws. Dionysus wept tears of wine in anguish for his activity at the afterimage of the admirable statue. The god's tears again decrepit the quartz purple.[26]

This allegory and its variations are not begin in classical sources. However, the titan Rhea does present Dionysus with an amethyst bean to bottle the wine-drinker's acumen in actual text.[27]

Other cultural associations

Tibetans accede amethyst angelic to the Buddha and accomplish adoration chaplet from it.[28] Amethyst is advised the birthstone of February.[29] In the Middle Ages, it was advised a attribute of ability and acclimated to adorn English regalia.[29] In the Old World, amethyst was advised one of the Basal gems, in that it was one of the bristles gemstones advised adored aloft all others, until ample deposits were begin in Brazil.

Value

Up until the 18th century, amethyst was included in the cardinal, or best valuable, gemstones (along with diamond, sapphire, ruby, and emerald). However, back the analysis of all-encompassing deposits in locations such as Brazil, it has absent best of its value.

Collectors attending for abyss of color, possibly with red flashes if cut conventionally.[30] As amethyst is readily accessible in ample structures the amount of the gem is not primarily authentic by carat weight; this is altered from best gemstones area the carat weight exponentially increases the amount of the stone. The better agency in the amount of amethyst is the blush displayed.[31]

The highest-grade amethyst (called "Deep Russian") is awfully attenuate and therefore, back one is found, its amount is abased on the appeal of collectors. It is, however, still orders of consequence cheaper than the highest-grade sapphires or rubies.

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.^[1] The term has largely fallen out of use.

The five traditional cardinal gems are:

• amethyst (purple) – Rare and precious in the Old World until large deposits were found in Brazil.
• diamond (white)
• emerald (green)
• ruby (red)
• sapphire (blue)

Emerald

Emerald is a gemstone and a array of the mineral azure (Be3Al2(SiO3)6) atramentous blooming by trace amounts of chromium and sometimes vanadium.[2] Azure has a acerbity of 7.5–8 on the Mohs scale.[2] Best emeralds are awful included,[3] so their courage (resistance to breakage) is classified as about poor. Emerald is a cyclosilicate.

Etymology

The chat "emerald" is acquired (via Old French: esmeraude and Middle English: emeraude), from Vulgar Latin: esmaralda/esmaraldus, a alternative of Latin smaragdus, which was a via Ancient Greek: σμάραγδος (smaragdos; "green gem") from a Semitic language.[4]

Properties free value

Cut emeralds

Emeralds, like all atramentous gemstones, are graded application four basal parameters–the four Cs of connoisseurship: color, clarity, cut and carat weight. Normally, in the allocation of atramentous gemstones, blush is by far the best important criterion. However, in the allocation of emeralds, accuracy is advised a abutting second. A accomplished emerald charge acquire not alone a authentic blooming blooming hue as declared below, but additionally a aerial amount of accuracy to be advised a top gemstone.[5]

In the 1960s, the American adornment industry afflicted the analogue of emerald to accommodate the blooming vanadium-bearing beryl. As a result, vanadium emeralds purchased as emeralds in the United States are not accustomed as such in the UK and Europe. In America, the acumen amid adequate emeralds and the new vanadium affectionate is generally reflected in the use of agreement such as "Colombian emerald".[6]

Color

In gemology,[7] blush is disconnected into three components: hue, saturation, and tone. Emeralds action in hues alignment from yellow-green to blue-green, with the primary hue necessarily actuality green. Chicken and dejected are the accustomed accessory hues begin in emeralds. Alone gems that are average to aphotic in accent are advised emeralds; light-toned gems are accustomed instead by the breed name blooming beryl. The finest emeralds are about 75% accent on a calibration breadth 0% accent is achromatic and 100% is blurred black. In addition, a accomplished emerald will be saturated and accept a hue that is ablaze (vivid). Gray is the accustomed assimilation modifier or affectation begin in emeralds; a grayish-green hue is a dull-green hue.[5]

Clarity

Brazilian emerald (grass-green array of the mineral beryl) in a quartz-pegmatite cast with archetypal hexagonal, bright crystals.[8]

Emeralds tend to accept abundant inclusions and surface-breaking fissures. Unlike diamonds, breadth the loupe standard, i.e. 10× magnification, is acclimated to brand clarity, emeralds are graded by eye. Thus, if an emerald has no arresting inclusions to the eye (assuming accustomed beheld acuity) it is advised flawless. Stones that abridgement credible breaking fissures are acutely attenuate and accordingly about all emeralds are advised ("oiled", see below) to enhance the credible clarity. The inclusions and fissures aural an emerald are sometimes declared as jardin (French for garden), because of their mossy appearance.[9] Imperfections are altered for anniversary emerald and can be acclimated to analyze a accurate stone. Eye-clean stones of a active primary blooming hue (as declared above), with no added than 15% of any accessory hue or aggregate (either dejected or yellow) of a medium-dark tone, command the accomplished prices.[5] The about non-uniformity motivates the acid of emeralds in cabochon form, rather than faceted shapes. Faceted emeralds are best frequently accustomed an egg-shaped cut, or the signature emerald cut, a ellipsoidal cut with facets about the top edge.

Treatments

Most emeralds are bashed as allotment of the post-lapidary process, in adjustment to ample in surface-reaching cracks so that accuracy and adherence are improved. Cedar oil, accepting a agnate refractive index, is generally acclimated in this broadly adopted practice. Added liquids, including constructed oils and polymers with refractive indexes abutting to that of emeralds, such as Opticon, are additionally used. These treatments are about activated in a exhaustion alcove beneath balmy heat, to accessible the pores of the bean and acquiesce the fracture-filling abettor to be captivated added effectively.[10] The U.S. Federal Barter Commission requires the acknowledgment of this analysis aback an oil advised emerald is sold.[11] The use of oil is adequate and abundantly accustomed by the gem trade, although oil advised emeralds are account abundant beneath than un-treated emeralds of agnate quality. Added treatments, for archetype the use of green-tinted oil, are not adequate in the trade.[12] Gems are graded on a four-step scale; none, minor, abstinent and awful enhanced. These categories reflect levels of enhancement, not clarity. A gem graded none on the accessory calibration may still display arresting inclusions. Laboratories administer these belief differently. Some gemologists accede the bald attendance of oil or polymers to aggregate enhancement. Others may avoid traces of oil if the attendance of the actual does not advance the attending of the gemstone.[13]

Emerald mines

A Colombian trapiche emerald

Emeralds in antique were mined in Egypt at locations on Mount Smaragdus aback 1500 BCE, and India, and Austria aback at atomic the 14th aeon CE.[14] The Egyptian mines were exploited on an automated calibration by the Roman and Byzantine Empires, and after by Islamic conquerors. Mining accomplished with the analysis of the Colombian deposits; alone charcoal remain.[15]

Colombia is by far the world's better ambassador of emeralds, basic 50–95% of the apple production, with the cardinal depending on the year, antecedent and grade.[16][17][18][19] Emerald assembly in Colombia has added acutely in the aftermost decade, accretion by 78% from 2000 to 2010.[20] The three capital emerald mining areas in Colombia are Muzo, Coscuez, and Chivor.[21] Attenuate "trapiche" emeralds are begin in Colombia, acclaimed by ray-like spokes of aphotic impurities.

Zambia is the world's additional better producer, with its Kafubu River breadth deposits (Kagem Mines) about 45 km (28 mi) southwest of Kitwe amenable for 20% of the world's assembly of gem-quality stones in 2004.[22] In the aboriginal bisected of 2011, the Kagem Mines produced 3.74 bags of emeralds.

Emeralds are begin all over the apple in countries such as Afghanistan, Australia, Austria, Brazil,[23] Bulgaria, Cambodia, Canada, China, Egypt, Ethiopia, France, Germany, India, Italy, Kazakhstan, Madagascar, Mozambique, Namibia, Nigeria, Norway, Pakistan, Russia, Somalia, South Africa, Spain, Switzerland, Tanzania, the United States, Zambia, and Zimbabwe.[1] In the US, emeralds accept been begin in Connecticut, Montana, Nevada, North Carolina, and South Carolina.[1] In Canada, in 1997 emeralds were apparent in the Yukon.[24]

Origin determinations

Since the access of apropos apropos design origins, analysis has been conducted to actuate if the mining area could be bent for an emerald already in circulation. Adequate analysis acclimated qualitative guidelines such as an emerald's color, appearance and affection of cutting, blazon of breach filling, and the animal origins of the artifacts address the mineral to actuate the emerald's abundance location. Added contempo studies application activity dispersive X-ray spectroscopy methods accept baldheaded trace actinic aspect differences amid emeralds, including ones mined in abutting adjacency to one another. American gemologist David Cronin and his colleagues accept abundantly advised the actinic signatures of emeralds consistent from aqueous dynamics and attenuate precipitation mechanisms, and their analysis approved the actinic accord of emeralds from the aforementioned mining area and the statistical differences that abide amid emeralds from altered mining locations, including those amid the three locations: Muzo, Coscuez, and Chivor, in Colombia, South America.[25]

Synthetic emerald

Emerald assuming its hexagonal structure

Both hydrothermal and flux-growth bolt accept been produced, and a adjustment has been developed for bearing an emerald overgrowth on achromatic beryl. The aboriginal commercially acknowledged emerald amalgam action was that of Carroll Chatham, acceptable involving a lithium vanadate alteration process, as Chatham's emeralds do not accept any baptize and accommodate traces of vanadate, molybdenum and vanadium.[26] The added ample ambassador of alteration emeralds was Pierre Gilson Sr., whose articles accept been on the bazaar aback 1964. Gilson's emeralds are usually developed on accustomed achromatic azure seeds, which are coated on both sides. Advance occurs at the amount of 1 mm per month, a archetypal seven-month advance run produces emerald crystals 7 mm thick.[27]

Hydrothermal constructed emeralds accept been attributed to IG Farben, Nacken, Tairus, and others, but the aboriginal satisfactory bartering artefact was that of Johann Lechleitner of Innsbruck, Austria, which appeared on the bazaar in the 1960s. These stones were initially awash beneath the names "Emerita" and "Symeralds", and they were developed as a attenuate band of emerald on top of accustomed achromatic azure stones. Later, from 1965 to 1970, the Linde Division of Union Carbide produced absolutely constructed emeralds by hydrothermal synthesis. According to their patents (attributable to E.M. Flanigen),[28] acerb altitude are capital to anticipate the chromium (which is acclimated as the colorant) from precipitating. Also, it is important that the silicon-containing comestible be kept abroad from the added capacity to anticipate nucleation and confine advance to the berry crystals. Advance occurs by a diffusion-reaction process, assisted by convection. The better ambassador of hydrothermal emeralds today is Tairus, which has succeeded in synthesizing emeralds with actinic agreement agnate to emeralds in acrid deposits in Colombia, and whose articles are appropriately accustomed as “Colombian created emeralds” or “Tairus created emeralds”.[29] Luminescence in ultraviolet ablaze is advised a added analysis aback authoritative a accustomed against constructed determination, as many, but not all, accustomed emeralds are apathetic to ultraviolet light. Abounding bolt are additionally UV inert.[30]

Emerald fabricated by hydrothermal synthesis

Synthetic emeralds are generally referred to as "created", as their actinic and gemological agreement is the aforementioned as their accustomed counterparts. The U.S. Federal Barter Commission (FTC) has actual austere regulations as to what can and what cannot be alleged a "synthetic" stone. The FTC says: "§ 23.23(c) It is arbitrary or ambiguous to use the chat "laboratory-grown", "laboratory-created", "[manufacturer name]-created", or "synthetic" with the name of any accustomed bean to call any industry artefact unless such industry artefact has about the aforementioned optical, physical, and actinic backdrop as the bean named."[11]

In ability and lore

Emerald is admired as the adequate birthstone for May as able-bodied as the adequate gemstone for the abstruse assurance of Cancer.[31]

One of the quainter anecdotes about emeralds was told by the 16th-century historian Brantôme, who referred to the abounding absorbing emeralds the Spanish beneath Cortez had brought aback to Europe from Latin America. On one of Cortez's best notable emeralds he had the argument engraved, Inter Natos Mulierum non sur-rexit ambassador ("Among those built-in of woman there hath not arisen a greater," Matthew 11:11) which referred to John the Baptist. Brantôme advised block such a admirable and simple artefact of attributes cursing and advised this act the account for Cortez's accident of an acutely adored fair (to which he committed a work, A admirable and incomparable pearl), and alike for the afterlife of King Charles IX of France, who died anon afterward.[32]

The arch celestial of one of India's best acclaimed temples, the Meenakshi Amman Temple in Madurai, is the goddess Meenakshi, whose idol is commonly anticipation to be fabricated of emerald.

Sapphire

Sapphire is a adored gemstone, a array of the mineral corundum, consisting of aluminum oxide (α-Al2O3) with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium. It is about blue, but accustomed "fancy" sapphires additionally action in yellow, purple, orange, and blooming colors; "parti sapphires" actualization two or added colors. Red corundum stones additionally action but are alleged rubies not sapphires.[2] Blush atramentous corundum may be classified either as bittersweet or azure depending on locale. Commonly, accustomed sapphires are cut and able into gemstones and beat in jewelry. They additionally may be created synthetically in laboratories for automated or adorning purposes in ample bright boules. Because of the arresting acerbity of sapphires – 9 on the Mohs calibration (the third hardest mineral, afterwards design at 10 and moissanite at 9.5) – sapphires are additionally acclimated in some non-ornamental applications, such as bittersweet optical components, high-durability windows, wristwatch crystals and movement bearings, and actual attenuate cyberbanking wafers, which are acclimated as the accurate substrates of special-purpose solid-state electronics such as dent circuits and GaN-based dejected LEDs.

Sapphire is the birthstone for September and the gem of the 45th anniversary. A azure ceremony occurs afterwards 65 years

Natural sapphires

An uncut, asperous chicken azure begin at the Spokane Azure Abundance abreast Helena, Montana

Sapphire is one of the two gem-varieties of corundum, the added actuality bittersweet (defined as corundum in a adumbration of red). Although dejected is the best-known azure color, they action in added colors, including gray and black, and they can be colorless. A pinkish orange array of azure is alleged padparadscha.

Significant azure deposits are begin in Australia, Afghanistan, Cambodia, Cameroon, China (Shandong), Colombia, Ethiopia, India (Kashmir), Kenya, Laos, Madagascar, Malawi, Mozambique, Myanmar (Burma), Nigeria, Rwanda, Sri Lanka, Tanzania, Thailand, United States (Montana) and Vietnam.[4]:431–707 Azure and rubies are about begin in the aforementioned bounded settings, but they about accept altered geological formations. For example, both bittersweet and azure are begin in Myanmar's Mogok Bean Tract, but the rubies anatomy in marble, while the azure forms in granitic pegmatites or corundum syenites.[4]:403–429

Every azure abundance produces a avant-garde ambit of quality, and agent is not a agreement of quality. For sapphire, Kashmir receives the accomplished premium, although Burma, Sri Lanka, and Madagascar additionally aftermath ample quantities of accomplished affection gems.[2]

The amount of accustomed sapphires varies depending on their color, clarity, size, cut, and all-embracing quality. Sapphires that are absolutely basic are account far added than those that accept been treated. Bounded agent additionally has a aloft appulse on price. For best gems of one carat or more, an absolute address from a admired chic such as American Gemological Laboratories (AGL), Gem Research Swisslab (GRS), GIA, Gübelin, Lotus Gemology, or SSEF, is about appropriate by buyers afore they will accomplish a purchase.[5]

Blue sapphire

Teardrop-shaped dejected sapphire

Gemstone blush can be declared in agreement of hue, saturation, and tone. Hue is frequently accepted as the "color" of the gemstone. Assimilation refers to the afterglow or accuracy of the hue, and accent is the animation to black of the hue.[4]:333–401 Dejected azure exists in assorted mixtures of its primary (blue) and accessory hues, assorted tonal levels (shades) and at assorted levels of assimilation (vividness).

Blue sapphires are evaluated based aloft the abstention of their dejected hue. Violet, and blooming are the best accepted accessory hues begin in dejected sapphires.[4]:333–401 The accomplished prices are paid for gems that are authentic dejected and of active saturation. Gems that are of lower saturation, or are too aphotic or too ablaze in accent are of beneath value. However, blush preferences are a claimed taste, like a acidity of ice cream.[4]:333–401

The 423-carat (84.6 g) Logan azure in the National Museum of Accustomed History, in Washington, D.C., is one of the bigger faceted gem-quality dejected sapphires in existence.

Dark dejected sapphire, apparently of Australian origin, assuming the ablaze credible afterglow archetypal of faceted corundum gemstones.

The 422.66-ct Siren of Serendip[6] in the Houston Museum of Accustomed Science is accession beauteous archetype of a Sri Lankan azure on accessible display.

Sapphires of added colors

Sapphires in colors added than dejected are alleged "fancy" or "parti colored" sapphires.[7]

Fancy sapphires are about begin in yellow, orange, green, brown, amethyst and violet hues.[8]

Particolored sapphires are those stones which affectation two or added colors aural a distinct stone.[8] Australia is the bigger antecedent of particolored sapphires; they are not frequently acclimated in boilerplate adornment and abide about unknown. Particolored sapphires cannot be created synthetically and alone action naturally.[citation needed]

Colorless sapphires accept historically been acclimated as design substitutes in jewelry.[8]

Pink sapphires

Pink sapphire

Pink sapphires action in shades from ablaze to aphotic pink, and deepen in blush as the abundance of chromium increases. The added the blush color, the college their budgetary value. In the United States, a minimum blush assimilation allegation be met to be alleged a ruby, contrarily the bean is referred to as a blush sapphire.[9]

Padparadscha

Faceted padparadscha

Padparadscha is a delicate, ablaze to average toned, pink-orange to orange-pink brave corundum, originally begin in Sri Lanka,[10] but additionally begin in deposits in Vietnam and genitalia of East Africa. Padparadscha sapphires are rare; the rarest of all is the absolutely accustomed variety, with no assurance of bogus treatment.[11]

The name is acquired from the Sanskrit "padma ranga" (padma = lotus; ranga = color), a blush affiliated to the lotus annual (Nelumbo nucifera).[12]

Among the adorned (non-blue) sapphires, accustomed padparadscha aback the accomplished prices. Aback 2001, added sapphires of this blush accept appeared on the bazaar as a aftereffect of bogus filigree circulation of beryllium.[13]

Star sapphire

Star sapphire

A brilliant azure is a blazon of azure that exhibits a star-like abnormality accepted as asterism; red stones are accepted as "star rubies". Brilliant sapphires accommodate intersecting needle-like inclusions afterward the basal bright anatomy that causes the actualization of a six-rayed "star"-shaped arrangement aback beheld with a distinct aerial ablaze source. The admittance is about the mineral rutile, a mineral composed primarily of titanium dioxide.[14] The stones are cut en cabochon, about with the centermost of the brilliant abreast the top of the dome. Occasionally, twelve-rayed stars are found, about because two altered sets of inclusions are begin aural the aforementioned stone, such as a aggregate of accomplished all-overs of rutile with baby platelets of hematite; the aboriginal after-effects in a blanched brilliant and the additional after-effects in a golden-colored star. During crystallization, the two types of inclusions become preferentially aggressive in altered admonition aural the crystal, thereby basic two six-rayed stars that are superimposed aloft ceremony added to anatomy a twelve-rayed star.[15] Misshapen stars or 12-rayed stars may additionally anatomy as a aftereffect of twinning. The inclusions can alternatively aftermath a "cat's eye" aftereffect if the girdle alike of the cabochon is aggressive alongside to the crystal's c-axis rather than erect to it. To get a cat's eye, the planes of exsolved inclusions allegation be acutely compatible and deeply packed. If the arch is aggressive in amid these two directions, an 'off-center' brilliant will be visible, account abroad from the aerial point of the dome.[4]:101

At 1404.49 carats, The Brilliant of Adam is claimed to be the bigger dejected brilliant sapphire, but whenever such claims are made, one should be accurate not to agree admeasurement with affection or value. The gem was mined in the burghal of Ratnapura, southern Sri Lanka.[16] The Atramentous Brilliant of Queensland, the additional bigger brilliant azure in the world, weighs 733 carats.[17] The Brilliant of India mined in Sri Lanka and acceptance 563.4 carats is anticipation to be the third-largest brilliant sapphire, and is currently on affectation at the American Museum of Accustomed History in New York City. The 182-carat Brilliant of Bombay, mined in Sri Lanka and amid in the National Museum of Accustomed History in Washington, D.C., is accession archetype of a ample dejected brilliant sapphire. The amount of a brilliant azure depends not alone on the weight of the stone, but additionally the anatomy color, visibility, and acuteness of the asterism. A accepted aberration fabricated by novices is to amount stones with able stars the highest. In fact, the blush of the bean has added appulse on the amount than the afterimage of the star. Aback added cellophane stones tend to accept bigger colors, the best big-ticket brilliant stones are semi-transparent "glass body" stones with active colors.[4]:348–350

Large rubies and sapphires

Large rubies and sapphires of poor accuracy are frequently acclimated with doubtable appraisals that awfully enlarge their value. This was the case of the "Life and Pride of America Brilliant Sapphire". About 1985, Roy Whetstine claimed to accept bought the 1905-ct bean for $10 at the Tucson gem show, but a anchorman credible that L.A. Ward of Fallbrook, CA, who acquainted it at the amount of $1200/ct, had acquainted accession bean of the exact aforementioned weight several years afore Whetstine claimed to accept begin it.[18]

Bangkok-based Lotus Gemology maintains an adapted advertisement of apple bargain annal of ruby, sapphire, and spinel. As of November 2019, no azure has anytime awash at bargain for added than $17,295,796.[19]

Color-change sapphire

A attenuate array of accustomed sapphire, accepted as color-change sapphire, exhibits altered colors in altered light. Blush change sapphires are dejected in alfresco ablaze and amethyst beneath beaming calm light, or blooming to gray-green in aurora and blush to reddish-violet in beaming light. Blush change sapphires arise from a array of locations, including Madagascar, Myanmar, Sri Lanka and Tanzania. Two types exist. The aboriginal actualization the chromium chromophore that creates the red blush of ruby, accumulated with the adamant + titanium chromophore that produces the dejected blush in sapphire. A added attenuate type, which comes from the Mogok breadth of Myanmar, actualization a vanadium chromophore, the aforementioned as is acclimated in Verneuil constructed color-change sapphire.

Virtually all gemstones that actualization the "alexandrite effect" (color change; a.k.a. 'metamerism') actualization agnate absorption/transmission actualization in the arresting spectrum. This is an assimilation bandage in the chicken (~590 nm), forth with valleys of manual in the blue-green and red. Appropriately the blush one sees depends on the ashen agreement of the ablaze source. Aurora is about counterbalanced in its ashen ability administration (SPD) and aback the animal eye is best acute to blooming light, the antithesis is angled to the blooming side. About beaming ablaze (including candle light) is heavily agee to the red end of the spectrum, appropriately angled the antithesis to red.[20]

Color-change sapphires atramentous by the Cr + Fe/Ti chromophores about change from dejected or violetish dejected to violet or purple. Those atramentous by the V chromophore can actualization a added arresting change, affective from blue-green to purple.

Certain constructed color-change sapphires accept a agnate blush change to the accustomed gemstone alexandrite and they are sometimes marketed as "alexandrium" or "synthetic alexandrite". However, the closing appellation is a misnomer: constructed color-change sapphires are, technically, not constructed alexandrites but rather alexandrite simulants. This is because 18-carat alexandrite is a array of chrysoberyl: not sapphire, but an absolutely altered mineral.[21]

Cause of color

Crystal anatomy of sapphire

Sapphire arena fabricated about 1940

Rubies are corundum with a ascendant red anatomy color. This is about acquired by traces of chromium (Cr3+) substituting for the (Al3+) ion in the corundum structure. The blush can be adapted by both adamant and trapped aperture blush centers.[22]

Unlike localized ("intra-atomic") assimilation of ablaze which causes blush for chromium and vanadium impurities, dejected blush in sapphires comes from intervalence allegation transfer, which is the alteration of an electron from one transition-metal ion to accession via the advice or valence band. The adamant can booty the anatomy Fe2+ or Fe3+, while titanium about takes the anatomy Ti4+. If Fe2+ and Ti4+ ions are commissioned for Al3+, localized areas of allegation alterity are created. An electron alteration from Fe2+ and Ti4+ can account a change in the valence accompaniment of both. Because of the valence change there is a specific change in activity for the electron, and electromagnetic activity is absorbed. The amicableness of the activity captivated corresponds to chicken light. Aback this ablaze is subtracted from adventure white light, the commutual blush dejected results. Sometimes aback diminutive agreement is altered in altered admonition there is consistent blue-green dichroism.

Purple sapphires accommodate trace amounts of chromium and adamant additional titanium and arise in a array of shades. Corundum that contains acutely low levels of chromophores is abreast colorless. Absolutely achromatic corundum about does not abide in nature. If trace amounts of adamant are present, a actual anemic chicken to blooming blush may be seen. However, if both titanium and adamant algae are present together, and in the actual valence states, the aftereffect is a dejected color.[23]

Intervalence allegation alteration is a action that produces a able atramentous actualization at a low allotment of impurity. While at atomic 1% chromium allegation be present in corundum afore the abysmal red bittersweet blush is seen, azure dejected is credible with the attendance of alone 0.01% of titanium and iron.

The best complete description of the causes of blush in corundum actual can be begin in Affiliate 4 of Bittersweet & Sapphire: A Gemologist's Guide (chapter authored by John Emmett, Emily Dubinsky and Richard Hughes).[4]:107–164

Treatments

Sapphires can be advised by several methods to enhance and advance their accuracy and color.[4]:197–247 It is accepted convenance to calefaction accustomed sapphires to advance or enhance their appearance. This is done by heating the sapphires in furnaces to temperatures amid 800 and 1,800 °C (1,470 and 3,270 °F) for several hours, or alike weeks at a time. Altered atmospheres may be used. Aloft heating, the bean becomes added dejected in color, but loses some of the rutile inclusions (silk). Aback aerial temperatures (1400 °C+) are used, exsolved rutile cottony is attenuated and it becomes bright beneath magnification. The titanium from the rutile enters solid band-aid and appropriately creates with adamant the dejected blush [24] The inclusions in accustomed stones are calmly credible with a jeweler's loupe. Affirmation of azure and added gemstones actuality subjected to heating goes aback at atomic to Roman times.[25] Un-heated accustomed stones are somewhat attenuate and will about be awash accompanied by a affidavit from an absolute gemological chic attesting to "no affirmation of calefaction treatment".

Yogo sapphire

Yogo sapphires do not charge calefaction alleviative because their cornflower dejected blush is adorable out of the ground; they are about chargeless of inclusions, and accept aerial compatible clarity.[26] Aback Intergem Bound began business the Yogo in the 1980s as the world's alone affirmed basic sapphire, calefaction assay was not frequently disclosed; by the backward 1980s, calefaction assay became a aloft issue.[27] At that time, abundant of all the world's sapphires were actuality acrimonious to enhance their accustomed color.[28] Intergem's business of affirmed basic Yogos set them adjoin abounding in the gem industry. This affair appeared as a front-page adventure in the Wall Street Journal on 29 August 1984 in an commodity by Bill Richards, Carats and Schticks: Azure Marketer Upsets The Gem Industry.[28] However, the better botheration the Yogo abundance faced was not antagonism from acrimonious sapphires, but the actuality that the Yogo stones could never aftermath quantities of azure aloft one carat afterwards faceting. As a result, it has remained a alcove product, with a bazaar that abundantly exists in the US.[4]:676–695

Lattice ('bulk') circulation treatments are acclimated to add algae to the azure to enhance color. This action was originally developed and patented by Linde Air assay of Union Carbide and complex diffusing titanium into constructed azure to alike out the dejected color.[29] It was afterwards activated to accustomed sapphire. Today, titanium circulation about uses a constructed achromatic azure base. The blush bandage created by titanium circulation is acutely attenuate (less than 0.5 mm). Appropriately repolishing can and does aftermath slight to cogent accident of color. Chromium circulation has been attempted, but was alone due to the apathetic circulation ante of chromium in corundum.

In the year 2000, beryllium diffused "padparadscha" atramentous sapphires entered the market. About beryllium is diffused into a azure beneath actual aerial heat, aloof beneath the melting point of the sapphire. Initially (c. 2000) orange sapphires were created, although now the action has been avant-garde and abounding colors of azure are about advised with beryllium. Due to the baby admeasurement of the beryllium ion, the blush assimilation is far greater than with titanium diffusion. In some cases, it may access the absolute stone. Beryllium-diffused orange sapphires may be difficult to detect, acute avant-garde actinic assay by gemological labs (e.g., Gübelin, SSEF, GIA, American Gemological Laboratories (AGL), Lotus Gemology.[5]

According to United States Federal Barter Commission guidelines, acknowledgment is appropriate of any approach of accessory that has a cogent aftereffect on the gem's value.[30]

There are several means of alleviative sapphire. Heat-treatment in a abbreviation or acerbic atmosphere (but afterwards the use of any added added impurities) is frequently acclimated to advance the blush of sapphires, and this action is sometimes accepted as "heating only" in the gem trade. In contrast, however, calefaction assay accumulated with the advised accession of assertive specific algae (e.g. beryllium, titanium, iron, chromium or nickel, which are captivated into the bright anatomy of the sapphire) is additionally frequently performed, and this action can be accepted as "diffusion" in the gem trade. However, admitting what the agreement "heating only" and "diffusion" ability suggest, both of these categories of assay absolutely absorb circulation processes.[31]

The best complete description of corundum treatments actual can be begin in Affiliate 6 of Bittersweet & Sapphire: A Gemologist's Guide (chapter authored by John Emmett, Richard Hughes and Troy R. Douthit).[4]:197–247

Mining

Sapphire from Madagascar

Sapphires are mined from alluvial deposits or from primary underground workings. Commercial mining locations for azure and bittersweet accommodate (but are not bound to) the afterward countries: Afghanistan, Australia, Myanmar/Burma, Cambodia, China, Colombia, India, Kenya, Laos, Madagascar, Malawi, Nepal, Nigeria, Pakistan, Sri Lanka, Tajikistan, Tanzania, Thailand, United States, and Vietnam. Sapphires from altered geographic locations may accept altered appearances or chemical-impurity concentrations, and tend to accommodate altered types of diminutive inclusions. Because of this, sapphires can be disconnected into three ample categories: archetypal metamorphic, non-classic metamorphic or magmatic, and archetypal magmatic.[32]

Sapphires from assertive locations, or of assertive categories, may be added commercially ambrosial than others,[33] decidedly archetypal metamorphic sapphires from Kashmir, Burma, or Sri Lanka that accept not been subjected to heat-treatment.[34][35][36]

The Logan sapphire, the Brilliant of India, The Brilliant of Adam and the Brilliant of Bombay arise from Sri Lankan mines. Madagascar is the apple baton in azure assembly (as of 2007) accurately its deposits in and about the boondocks of Ilakaka.[37] Prior to the aperture of the Ilakaka mines, Australia was the bigger ambassador of sapphires (such as in 1987).[38] In 1991 a new antecedent of sapphires was credible in Andranondambo, southern Madagascar. That breadth has been exploited for its sapphires started in 1993, but it was about alone aloof a few years later—because of the difficulties in convalescent sapphires in their bedrock.[39]

In North America, sapphires accept been mined mostly from deposits in Montana: fancies forth the Missouri River abreast Helena, Montana, Dry Cottonwood Creek abreast Deer Lodge, Montana, and Rock Creek abreast Philipsburg, Montana. Accomplished dejected Yogo sapphires are begin at Yogo Gulch west of Lewistown, Montana.[27] A few gem-grade sapphires and rubies accept additionally been begin in the breadth of Franklin, North Carolina.[40]

The azure deposits of Kashmir are able-bodied accepted in the gem industry, although their aiguille assembly took abode in a about abbreviate aeon at the end of the nineteenth and aboriginal twentieth centuries.[4]:463–482 They accept a above active dejected hue, accompanying with a abstruse and about asleep quality, declared by some gem enthusiasts as ‘blue velvet”. Kashmir-origin contributes advisedly to the amount of a sapphire, and best corundum of Kashmir agent can be readily articular by its appropriate cottony actualization and aberrant hue.[41][42] The different dejected appears bright beneath any affectionate of light, clashing non-Kashmir sapphires which may arise purplish or grayish in comparison.[43] Sotheby's has been in the beginning administering record-breaking sales of Kashmir sapphires worldwide. In October 2014, Sotheby's Hong Kong accomplished afterwards per-carat amount annal for Kashmir sapphires – aboriginal with the 12.00 carat Cartier azure arena at US$193,975 per carat, afresh with a 17.16 carat azure at US$236,404, and afresh in June 2015 aback the per-carat bargain almanac was set at US$240,205.[44] At present, the apple almanac price-per-carat for azure at bargain is captivated by a azure from Kashmir in a ring, which awash in October 2015 for about US$242,000 per carat (HK$52,280,000 in total, including buyer's premium, or added than US$6.74 million).[44]

Synthetic sapphire

Synthetic sapphire

In 1902, the French chemist Auguste Verneuil appear a action for bearing constructed bittersweet crystals.[45] In the flame-fusion (Verneuil process), accomplished alumina crumb is added to an oxyhydrogen flame, and this is directed bottomward adjoin a bowl pedestal.[46] Afterward the acknowledged amalgam of ruby, Verneuil focussed his efforts on sapphire. Amalgam of dejected azure came in 1909, afterwards actinic analyses of azure appropriate to Verneuil that adamant and titanium were the account of the dejected color. Verneuil patented the action of bearing constructed dejected azure in 1911.[47][4]:254–255

The key to the action is that the alumina crumb does not cook as it avalanche through the flame. Instead it forms a sinter cone on the pedestal. Aback the tip of that cone alcove the hottest allotment of the flame, the tip melts. Appropriately the bright advance is started from a tiny point, ensuring basal strain.

Next, added oxygen is added to the flame, causing it to bake hardly hotter. This expands the growing bright laterally. At the aforementioned time, the basement is bargain at the aforementioned amount that the bright grows vertically. The alumina in the blaze is boring deposited, creating a bead shaped "boule" of azure material. This footfall is connected until the adapted admeasurement is reached, the blaze is shut off and the bright cools. The now continued bright contains a lot of ache due to the aerial thermal acclivity amid the blaze and surrounding air. To absolution this strain, the now finger-shaped bright will be broke with a blade to breach it into two halves.[4]:249–309

Due to the vertical layered advance of the bright and the arced aerial advance credible (which starts from a drop), the crystals will affectation arced advance curve afterward the top credible of the boule. This is in adverse to accustomed corundum crystals, which affection angular advance curve accretion from a distinct point and afterward the collapsed bright faces.[48]

Dopants

Chemical dopants can be added to actualize bogus versions of the ruby, and all the added accustomed colors of sapphire, and in addition, added colors never credible in geological samples. Bogus azure actual is identical to accustomed sapphire, except it can be fabricated afterwards the flaws that are begin in accustomed stones. The disadvantage of the Verneuil action is that the developed crystals accept aerial centralized strains. Abounding methods of accomplishment azure today are variations of the Czochralski process, which was invented in 1916 by Polish chemist Jan Czochralski.[49] In this process, a tiny azure berry bright is biconcave into a affliction fabricated of the adored metal iridium or molybdenum,[50] absolute aqueous alumina, and afresh boring aloof advancement at a amount of 1 to 100 mm per hour. The alumina crystallizes on the end, creating continued carrot-shaped boules of ample admeasurement up to 200 kg in mass.[51]

Other advance methods

Synthetic azure is additionally produced industrially from agglomerated aluminum oxide, sintered and alloyed (such as by hot isostatic pressing) in an apathetic atmosphere, acquiescent a cellophane but hardly absorptive polycrystalline product.[52]

In 2003, the world's assembly of constructed azure was 250 bags (1.25 × 109 carats), mostly by the United States and Russia.[53][54] The availability of bargain constructed azure apart abounding automated uses for this different material.

Applications

Windows

Cermax xenon arc lamp with constructed azure achievement window

Synthetic sapphire—sometimes referred to as azure glass—is frequently acclimated as a window material, because it is both awful cellophane to wavelengths of ablaze amid 150 nm (UV) and 5500 nm (IR) (the arresting spectrum extends about 380 nm to 750 nm[55]), and abnormally scratch-resistant.[56][57]

The key allowances of azure windows are:

Very avant-garde optical manual bandage from UV to near-infrared, (0.15–5.5 µm)

Significantly stronger than added optical abstracts or accepted bottle windows

Highly aggressive to abrading and chafe (9 on the Mohs calibration of mineral acerbity scale, the 3rd hardest accustomed actuality abutting to moissanite and diamonds)[41]

Extremely aerial melting temperature (2030 °C)

Single bright azure boule developed by the Kyropoulos method. About 200 millimetres (8 in) in diameter, acceptance about 30 kg (66 lb). (A additional boule is arresting in the background.)

Some sapphire-glass windows are fabricated from authentic azure boules that accept been developed in a specific bright orientation, about forth the optical axis, the c-axis, for minimum birefringence for the application.[58][59]

The boules are broken up into the adapted window array and assuredly able to the adapted credible finish. Azure optical windows can be able to a avant-garde ambit of credible finishes due to its bright anatomy and its hardness. The credible finishes of optical windows are frequently alleged out by the scratch-dig blueprint in accordance with the globally adopted MIL-O-13830 specification.[clarification needed]

The azure windows are acclimated in both aerial burden and exhaustion accommodation for spectroscopy, crystals in assorted watches, and windows in grocery abundance barcode scanners aback the material's aberrant acerbity and courage makes it actual aggressive to scratching.[53]

It is acclimated for end windows on some activating laser tubes as its wide-band accuracy and thermal application acquiesce it to handle actual aerial ability densities in the infra-red or UV spectrum afterwards aspersing due to heating.

Along with zirconia and aluminum oxynitride, constructed azure is acclimated for blast aggressive windows in armored cartage and assorted aggressive anatomy armor suits, in affiliation with composites.

One blazon of xenon arc lamp – originally alleged the "Cermax" and now accepted generically as the "ceramic anatomy xenon lamp" – uses azure bright achievement windows. This artefact tolerates college thermal endless and appropriately college achievement admiral aback compared with accepted Xe lamps with authentic silica window.[60][61]

As substrate for semiconducting circuits

Main article: silicon on sapphire

Thin azure wafers were the aboriginal acknowledged use of an accurate substrate aloft which to drop silicon to accomplish the dent circuits accepted as silicon on azure or "SOS"; now added substrates can additionally be acclimated for the chic of circuits accepted added about as silicon on insulator. Besides its accomplished electrical accurate properties, azure has aerial thermal conductivity. CMOS chips on azure are abnormally advantageous for high-power radio-frequency (RF) applications such as those begin in cellular telephones, public-safety bandage radios, and accessory advice systems. "SOS" additionally allows for the caked affiliation of both agenda and analog dent all on one IC chip, and the architecture of acutely low ability circuits.

In one process, afterwards distinct bright azure boules are grown, they are core-drilled into annular rods, and wafers are afresh broken from these cores.[citation needed]

Wafers of single-crystal azure are additionally acclimated in the semiconductor industry as substrates for the advance of accessories based on gallium nitride (GaN). The use of azure decidedly reduces the cost, because it has about one-seventh the amount of germanium. Gallium nitride on azure is frequently acclimated in dejected light-emitting diodes (LEDs).[62]

In lasers

The aboriginal laser was fabricated with a rod of constructed ruby. Titanium-sapphire lasers are accepted due to their about attenuate accommodation to be acquainted to assorted wavelengths in the red and near-infrared arena of the electromagnetic spectrum. They can additionally be calmly mode-locked. In these lasers a synthetically produced azure bright with chromium or titanium algae is ablaze with acute ablaze from a appropriate lamp, or accession laser, to actualize angry emission.

In endoprostheses

Monocrystalline azure is adequately biocompatible and the awfully low abrasion of sapphire–metal pairs has led to the addition (in Ukraine) of azure monocrystals for hip collective endoprostheses.[63]

Historical and cultural references

Etymologically, the English chat "sapphire" derives from French saphir, from Latin sapphirus, sappirus from Greek σαπφειρος (sappheiros) from Hebrew סַפִּיר (sappir). Some linguists adduce that the semitic (e.g. Hebrew) agreement acquire from Sanskrit Sanipriya (शनिप्रिय), from "sani" (शनि) acceptation "Saturn" and "priyah" (प्रिय), dear, i.e. actually "sacred to Saturn".[64]

A acceptable Hindu acceptance holds that the azure causes the planet Saturn (Shani) to be favorable to the wearer.[65]

The Greek appellation for azure absolutely acceptable was instead acclimated to accredit to lapis lazuli.[64]

During the Medieval Ages, European lapidaries came to accredit to dejected corundum bright by "sapphire", a acquired of the Latin chat for blue: "sapphirus".[66]

The azure is the acceptable allowance for a 45th bells anniversary.[67]

A azure ceremony occurs afterwards 65 years. Queen Elizabeth II apparent her azure ceremony in 2017.[3]

The azure is the birthstone of September.

An Italian superstition holds that sapphires are amulets adjoin eye problems, and melancholy.[68]

Pope Innocent III assured that rings of bishops should be fabricated of authentic gold, set with an unengraved sapphire, as possessing the virtues and qualities capital to its aristocratic position as a allowance of secrets, for there be abounding things "that a priest conceals from the senses of the barnyard and beneath intelligent; which he keeps bound up as it were beneath seal.

Ruby

A bittersweet is a blush to blood-red coloured gemstone, a array of the mineral corundum (aluminium oxide). Added varieties of gem-quality corundum are alleged sapphires. Bittersweet is one of the adequate basal gems, calm with amethyst, sapphire, emerald, and diamond.[3] The chat bittersweet comes from ruber, Latin for red. The blush of a bittersweet is due to the aspect chromium.

Some gemstones that are bargain or historically alleged rubies, such as the Black Prince's Bittersweet in the British Imperial Accompaniment Crown, are absolutely spinels. These were already accepted as "Balas rubies".

The affection of a bittersweet is bent by its color, cut, and clarity, which, forth with carat weight, affect its value. The brightest and best admired adumbration of red alleged blood-red or pigeon blood, commands a ample aberrant over added rubies of agnate quality. Afterwards blush follows clarity: agnate to diamonds, a bright bean will command a premium, but a bittersweet afterwards any needle-like rutile inclusions may announce that the bean has been treated. Bittersweet is the adequate birthstone for July and is usually pinker than garnet, although some rhodolite garnets accept a agnate pinkish hue to best rubies. The world's best admired bittersweet to be awash at bargain is the Sunrise Ruby.

Physical properties

Crystal anatomy of rubies

Rubies accept a acerbity of 9.0 on the Mohs calibration of mineral hardness. Among the accustomed gems alone moissanite and design are harder, with design accepting a Mohs acerbity of 10.0 and moissanite falling about in amid corundum (ruby) and design in hardness. Sapphire, ruby, and authentic corundum are α-alumina, the best abiding anatomy of Al2O3, in which 3 electrons leave anniversary aluminium ion to accompany the approved octahedral accumulation of six adjacent O2− ions; in authentic corundum this leaves all of the aluminium ions with a actual abiding agreement of no unpaired electrons or bare activity levels, and the bright is altogether colorless.

Crystal anatomy of bittersweet assuming the barter of Al3+ ions (blue) with Cr3+ (red). The barter body of Cr3+ ions in this archetypal is about 2%, approximating the best doping commonly encountered.[4]

When a chromium atom replaces an casual aluminium atom, it too loses 3 electrons to become a chromium3+ ion to advance the allegation antithesis of the Al2O3 crystal. However, the Cr3+ ions are beyond and accept electron orbitals in adapted admonition than aluminium. The octahedral adjustment of the O2− ions is distorted, and the activity levels of the adapted orbitals of those Cr3+ ions are hardly adapted because of the admonition to the O2− ions.[5] Those activity differences accord to assimilation in the ultraviolet, violet, and yellow-green regions of the spectrum.

Transmittance of bittersweet in optical and near-IR spectra. Note the two ample violet and yellow-green assimilation bands and one attenuated assimilation bandage at the amicableness of 694 nm, which is the amicableness of the bittersweet laser.

If one percent of the aluminium ions are replaced by chromium in ruby, the yellow-green assimilation after-effects in a red blush for the gem.[5] Additionally, assimilation at any of the aloft wavelengths stimulates beaming discharge of 694-nanometer-wavelength red light, which adds to its red blush and perceived luster.

After arresting short-wavelength light, there is a abbreviate breach of time aback the bright filigree of bittersweet is in an aflame accompaniment afore fluorescence occurs. If 694-nanometer photons canyon through the bright during that time, they can activate added beaming photons to be emitted in-phase with them, appropriately deepening the acuteness of that red light. By alignment mirrors or added agency to canyon emitted ablaze again through the crystal, a bittersweet laser in this way produces a actual aerial acuteness of articular red light.

All accustomed rubies accept imperfections in them, including blush algae and inclusions of rutile all-overs accepted as "silk". Gemologists use these aggravate inclusions begin in accustomed rubies to analyze them from synthetics, simulants, or substitutes. Usually, the asperous bean is acrimonious afore cutting. These days, about all rubies are advised in some form, with calefaction analysis actuality the best accepted practice. Untreated rubies of aerial affection command a ample premium.

Some rubies appearance a three-point or six-point asterism or "star". These rubies are cut into cabochons to affectation the aftereffect properly. Asterisms are best arresting with a single-light antecedent and move beyond the bean as the ablaze moves or the bean is rotated. Such furnishings action aback ablaze is reflected off the "silk" (the structurally aggressive rutile aggravate inclusions) in a assertive way. This is one archetype breadth inclusions access the amount of a gemstone. Furthermore, rubies can appearance blush changes—though this occurs actual rarely—as able-bodied as chatoyancy or the "cat's eye" effect.

Ruby vs. blush sapphire

Generally, gemstone-quality corundum in all shades of red, including pink, are alleged rubies.[6][7] However, in the United States, a minimum blush assimilation charge be met to be alleged a ruby; otherwise, the bean will be alleged a blush sapphire.[6] Drawing a acumen amid rubies and blush sapphires is about new, accepting arisen age-old in the 20th century. Often, the acumen amid bittersweet and blush azure is not bright and can be debated.[8] As a aftereffect of the adversity and subjectiveness of such distinctions, barter organizations such as the International Black Gemstone Association (ICGA) accept adopted the broader analogue for bittersweet which encompasses its lighter shades, including pink.[9][10]

Occurrence and mining

Historically, rubies accept been mined in Thailand, in the Pailin and Samlout District of Cambodia, as able-bodied as in Afghanistan, Australia, Brazil, Colombia, India, Namibia, Japan, and Scotland; afterwards the Additional Apple War bittersweet deposits were begin in Madagascar, Nepal, Pakistan, Tajikistan, Tanzania, and Vietnam.[11]

The Republic of North Macedonia is the alone country in acreage Europe to accept artlessly occurring rubies. They can mainly be begin about the burghal of Prilep. Macedonian rubies accept a altered raspberry color. The bittersweet is additionally included on the Macedonian covering of arms.[12] A few rubies accept been begin in the U.S. states of Montana, North Carolina, South Carolina and Wyoming.

Spinel, addition red gemstone, is sometimes begin forth with rubies in the aforementioned gem alluvium or marble. Red spinels may be mistaken for rubies by those defective acquaintance with gems. However, the finest red spinels can accept ethics abutting that of an boilerplate ruby.[13]

The Mogok Valley in Upper Myanmar (Burma) was for centuries the world's capital antecedent for rubies. That arena has produced some aberrant rubies, about in contempo years few adequate rubies accept been found. In axial Myanmar, the breadth of Mong Hsu began bearing rubies during the 1990s and rapidly became the world's capital bittersweet mining area. The best afresh begin bittersweet drop in Myanmar is in Namya (Namyazeik) amid in the arctic accompaniment of Kachin.

In Pakistani Kashmir there are all-inclusive accurate affluence of millions of rubies, account up to bisected a billion dollars.[14] However, as of 2017 there was alone one abundance (at Chitta Katha) due to abridgement of investment.[15] In Afghanistan, rubies are mined at Jegdalek.[16]

Factors affecting value

Rubies, as with added gemstones, are graded appliance acceptance accepted as the four Cs, namely color, cut, accuracy and carat weight. Rubies are additionally evaluated on the base of their geographic origin.

Color: In the appraisal of black gemstones, blush is the best important factor. Blush divides into three components: hue, assimilation and tone. Hue refers to blush as we commonly use the term. Cellophane gemstones action in the authentic ashen hues of red, orange, yellow, green, blue, violet.[17] In nature, there are rarely authentic hues, so aback speaking of the hue of a gemstone, we allege of primary and accessory and sometimes tertiary hues. Bittersweet is authentic to be red. All added hues of the gem breed corundum are alleged sapphire. Bittersweet may display a ambit of accessory hues, including orange, purple, violet, and pink.

Treatments and enhancements

Improving the affection of gemstones by alleviative them is accepted practice. Some treatments are acclimated in about all cases and are accordingly advised acceptable. During the backward 1990s, a ample accumulation of bargain abstracts acquired a abrupt billow in accumulation of heat-treated rubies, arch to a bottomward burden on bittersweet prices.

Improvements acclimated accommodate blush alteration, convalescent accuracy by abandoning rutile inclusions, healing of fractures (cracks) or alike absolutely bushing them.

The best accepted analysis is the appliance of heat. Best rubies at the lower end of the bazaar are calefaction advised to advance color, abolish amethyst tinge, dejected patches, and silk. These calefaction treatments about action about temperatures of 1800 °C (3300 °F).[18] Some rubies abide a action of low tube heat, aback the bean is acrimonious over charcoal of a temperature of about 1300 °C (2400 °F) for 20 to 30 minutes. The cottony is partially broken, and the blush is improved.

Another treatment, which has become added common in contempo years, is advance bottle filling. Bushing the fractures central the bittersweet with advance bottle (or a agnate material) badly improves the accuracy of the stone, authoritative ahead clashing rubies fit for applications in jewelry.[19] The action is done in four steps:

The asperous stones are pre-polished to eradicate all apparent algae that may affect the process

The asperous is bankrupt with hydrogen fluoride

The aboriginal heating action during which no fillers are added. The heating action eradicates algae central the fractures. Although this can be done at temperatures up to 1400 °C (2500 °F) it best acceptable occurs at a temperature of about 900 °C (1600 °F) aback the rutile cottony is still intact.

The additional heating action in an electrical oven with adapted actinic additives. Adapted solutions and mixes accept apparent to be successful, about mostly lead-containing glass-powder is acclimated at present. The bittersweet is biconcave into oils, again covered with powder, anchored on a asphalt and placed in the oven breadth it is acrimonious at about 900 °C (1600 °F) for one hour in an acerbic atmosphere. The orange black crumb transforms aloft heating into a cellophane to yellow-colored paste, which fills all fractures. Afterwards cooling the blush of the adhesive is absolutely cellophane and badly improves the all-embracing accuracy of the ruby.[20]

If a blush needs to be added, the bottle crumb can be "enhanced" with chestnut or added metal oxides as able-bodied as elements such as sodium, calcium, potassium etc.

The additional heating action can be again three to four times, alike applying adapted mixtures.[21] Aback adornment absolute rubies is acrimonious (for repairs) it should not be coated with boracic acerbic or any added substance, as this can compose the surface; it does not accept to be "protected" like a diamond.

The analysis can be articular by acquainted bubbles in cavities and fractures appliance a 10× loupe.[22]

Synthetic and apery rubies

Artificial bittersweet below a accustomed ablaze (top) and below a blooming laser ablaze (bottom). Red ablaze is emitted

In 1837, Gaudin fabricated the aboriginal complete rubies by fusing potash alum at a aerial temperature with a little chromium as a pigment. In 1847, Ebelmen fabricated white azure by fusing alumina in boric acid. In 1877, Edmond Frémy and automated glass-maker Charles Feil fabricated bright corundum from which baby stones could be cut. In 1887, Fremy and Auguste Verneuil bogus bogus bittersweet by fusing BaF2 and Al2O3 with a little chromium at red heat. In 1903, Verneuil appear he could aftermath complete rubies on a bartering calibration appliance this blaze admixture process, after additionally accepted as the Verneuil process.[23] By 1910, Verneuil's class had broadcast into a 30 boiler assembly facility, with anniversary gemstone assembly accepting accomplished 1,000 kilograms (2,000 lb) in 1907.

Other processes in which complete rubies can be produced are through Czochralski's affairs process, alteration process, and the hydrothermal process. Best complete rubies arise from blaze fusion, due to the low costs involved. Complete rubies may accept no imperfections arresting to the naked eye but deepening may acknowledge arced striae and gas bubbles. The below the cardinal and the below accessible the imperfections, the added admired the bittersweet is; unless there are no imperfections (i.e., a absolute ruby), in which case it will be doubtable of actuality artificial. Dopants are added to some bogus rubies so they can be articular as synthetic, but best charge gemological testing to actuate their origin.

Synthetic rubies accept abstruse uses as able-bodied as gemological ones. Rods of complete bittersweet are acclimated to accomplish bittersweet lasers and masers. The aboriginal alive laser was fabricated by Theodore H. Maiman in 1960.[24] Maiman acclimated a solid-state light-pumped complete bittersweet to aftermath red laser ablaze at a amicableness of 694 nanometers (nm). Bittersweet lasers are still in use. Rubies are additionally acclimated in applications breadth aerial acerbity is appropriate such as at wear-exposed locations in avant-garde automated clockworks, or as scanning delving tips in a alike barometer machine.

Imitation rubies are additionally marketed. Red spinels, red garnets, and black bottle accept been falsely claimed to be rubies. Imitations go aback to Roman times and already in the 17th aeon techniques were developed to blush antithesis red—by afire scarlet absolute in the basal allotment of the furnace—which was again placed below the apery stone.[25] Barter agreement such as balas bittersweet for red spinel and rubellite for red tourmaline can mislead biting buyers. Such agreement are accordingly beat from use by abounding gemological associations such as the Class Manual Harmonisation Committee (LMHC).

Records and acclaimed rubies

Rubies at the National Museum of Accustomed History, Washington, D.C., USA

The Smithsonian's National Museum of Accustomed History in Washington, D.C. has some of the world's better and finest bittersweet gemstones. The 23.1-carat (4.62 g) Burmese ruby, set in a platinum arena with diamonds, was donated by agent and philanthropist Peter Buck in anamnesis of his backward wife Carmen Lúcia. This gemstone displays a abundantly saturated red blush accumulated with an aberrant transparency. The cautiously ample cut provides active red reflections. The bean was mined from the Mogok arena of Burma (now Myanmar) in the 1930s.[26]

In 2007 the London jeweler Garrard & Co featured on their website a heart-shaped 40.63-carat ruby.[27]

On December 13/14, 2011 Elizabeth Taylor's complete jewellery accumulating was auctioned by Christie's. Several ruby-set pieces were included in the sale, conspicuously a arena set with an 8.24 ct gem that bankrupt the 'price-per-carat' almanac for rubies ($512,925 per carat, i.e. over $4.2 actor in total),[28] and a necklace[29] that awash for over $3.7 million.

The Liberty Bell Bittersweet is the better mined bittersweet in the world. It was baseborn in a break-in in 2011.[30]

The Sunrise Bittersweet is the world's best big-ticket ruby, best big-ticket coloured gemstone, and best big-ticket gemstone added than a diamond. In May 2015, it awash at bargain in Switzerland to an bearding client for US$30 million.[31]

A complete bittersweet bright became the accretion average in the world's aboriginal optical laser, conceived, advised and complete by Theodore H. "Ted" Maiman, on 16 May 1961 at Hughes Research Laboratories.[24][32] The abstraction of electromagnetic radiation addition through the apparatus of angry discharge had already been auspiciously approved in the class by way of the maser, appliance added abstracts such as ammonia and, later, ruby, but the bittersweet laser was the aboriginal accessory to assignment at optical (694.3 nm) wavelengths. Maiman's ancestor laser is still in alive order.

The Bittersweet Eye Amulet from Mesopotamia, Adilnor Collection, Sweden.

Historical and cultural references

An aboriginal recorded carriage and trading of rubies arises in the abstract on the North Cottony Road of China, wherein about 200 BC rubies were agitated forth this age-old trackway affective westward from China.[33]

Rubies accept consistently been captivated in aerial admire in Asian countries. They were acclimated to accessory armor, scabbards, and harnesses of noblemen in India and China. Rubies were laid below the foundation of barrio to defended adequate affluence to the structure.

A adequate Hindu abstruse acceptance holds rubies as the "gemstone of the Sun and additionally the adorable celestial Surya, the baton of the nine adorable bodies (Navagraha)." The acceptance is that adherent and cutting rubies causes the Sun to be favorable to the wearer. [34]

See also