Amethyst is aviolet variety ofquartz. The name comes from theKoine Greekαμέθυστοςamethystos fromα-a-, "not" andμεθύσκω (Ancient Greek)methysko /μεθώmetho (Modern Greek), "intoxicate", a reference to the belief that the stone protected its owner fromdrunkenness.[1]Ancient Greeks wore amethyst and carveddrinking vessels from it in the belief that it would prevent intoxication.
Amethyst is a violet variety ofquartz (SiO 2) and owes its violet color toirradiation, impurities ofiron (Fe3+ ) and in some cases othertransition metals, and the presence of other trace elements, which result in complex crystal lattice substitutions.[2][3][4]The irradiation causes the ironFe3+ ions that replace Si in the lattice to lose an electron and form a[FeO 4]0 color center.[5]Amethyst is a three-dimensional network of tetrahedra where the silicon atoms are in the center and are surrounded by four oxygen atoms located at the vertices of atetrahedron. This structure is quite rigid and results in quartz's hardness and resistance to weathering. Thehardness of the mineral is the same as quartz, thus making it suitable for use in jewelry.
Amethyst occurs in primaryhues from a light lavender or pale violet to a deep purple. Amethyst may exhibit one or both secondary hues, red and blue.[6]High-quality amethyst can be found inSiberia,Sri Lanka,Brazil,Uruguay, and the Far East. The ideal grade, called "Deep Siberian", has a primary purple hue of around 75–80%, with 15–20% blue and (depending on the light source) red secondary hues.[7]"Rose de France" is defined by its markedly light shade of thepurple, reminiscent of alavender /lilac shade. These pale colors were once considered undesirable, but have recently become popular due to intensive marketing.[8]
Green quartz is sometimes calledgreen amethyst; the scientific name isprasiolite.[9]Other names for green quartz arevermarine andlime citrine.
Amethyst frequently shows color zoning, with the most intense color typically found at the crystal terminations. One ofgem cutters' tasks is to make a finished product with even color. Sometimes, only a thin layer of a natural, uncut amethyst is violet colored, or the color is very uneven. The uncut gem may have only a small portion that is suitable for faceting.[10][11]
Natural purple/violet amethyst
Heat-treated amethyst
The color of amethyst has been demonstrated to result from substitution byirradiation of trivalent iron (Fe3+) for silicon in the structure,[4][12] in the presence of trace elements of large ionic radius,[3] and to a certain extent, the amethyst color can naturally result from displacement oftransition elements even if the iron concentration is low. Natural amethyst isdichroic in reddish violet and bluish violet,[4] but when heated, turns yellow-orange, yellow-brown, or dark brownish and may resemblecitrine,[13] but loses its dichroism, unlike genuine citrine. When partially heated, amethyst can result inametrine.
Amethyst can fade in tone if overexposed to light sources, and can be artificially darkened with adequate irradiation.[4] It does notfluoresce under either short-wave or long-waveUV light.
Amethyst is found in many locations around the world. Between 2000 and 2010, the greatest production was fromMarabá andPau d'Arco, Pará, and theParaná Basin, Rio Grande do Sul, Brazil; Sandoval,Santa Cruz, Bolivia; Artigas, Uruguay;Kalomo, Zambia; andThunder Bay, Ontario. Lesser amounts are found in many other locations in Africa, Brazil, Spain, Argentina, Russia, Afghanistan, South Korea, Mexico, and the United States.[14]
Amethyst is produced in abundance in the state ofRio Grande do Sul in Brazil where it occurs in largegeodes withinvolcanic rocks.[15][16][17][18]Many of the hollow agates of southwesternBrazil andUruguay contain a crop of amethyst crystals in the interior.Artigas, Uruguay and neighboring Brazilian state Rio Grande do Sul are large world producers, with lesser quantities mined inMinas Gerais andBahia states.[14]
An amethystgeode that formed when largecrystals grew in open spaces inside the rock
The largest amethyst geode found as of 2007 was theEmpress of Uruguay, found in Artigas, Uruguay in 2007. It stands at a height of 3.27 meters, lies open along its length, and weighs 2.5 tons.
Amethyst is also found and mined inSouth Korea.[19] The large opencast amethyst vein atMaissau, LowerAustria, was historically important,[1] but is no longer included among significant producers.[14] Much fine amethyst comes fromRussia, especially near Mursinka in theEkaterinburg district, where it occurs indrusy cavities ingraniticrocks.[1][14] Amethyst was historically mined in many localities in southIndia,[1] though these are no longer significant producers.[14] One of the largest global amethyst producers isZambia in southernAfrica, with an annual production around 1000 tons.[20]
Amethyst occurs at many localities in the United States. The most important production is at Four Peaks,Gila andMaricopa Counties, Arizona, and Jackson's Crossroads,Wilkes County, Georgia.[14]
Amethyst is relatively common in the Canadian provinces ofOntario andNova Scotia. The largest amethyst mine in North America is located in Thunder Bay, Ontario.[14]
Theancient Greeks believed amethyst gems could prevent intoxication,[23]while medieval European soldiers wore amethystamulets as protection in battle in the belief that amethysts heal people and keep them cool-headed.[24](p 77)Beads of amethyst were found inAnglo-Saxon graves in England.[25]Anglican bishops wear anepiscopal ring often set with an amethyst, an allusion to the description of the Apostles as "not drunk" atPentecost in Acts 2:15.[26]
A largegeode, or "amethyst-grotto", from near Santa Cruz in southernBrazil was presented at a 1902 exhibition inDüsseldorf, Germany.[1]
Synthetic (laboratory-grown) amethyst is produced by a synthesis method called hydrothermal growth, which grows the crystals inside a high-pressure autoclave.
Synthetic amethyst is made to imitate the best quality amethyst. Its chemical and physical properties are the same as those of natural amethyst, and it cannot be differentiated with absolute certainty without advanced gemmological testing (which is often cost-prohibitive). One test based on "Brazil law twinning" (a form ofquartz twinning where right- and left-hand quartz structures are combined in a single crystal[27]) can be used to identify most synthetic amethyst rather easily. Synthesizing twinned amethyst is possible, but this type is not available in large quantities in the market.[7]
Treated amethyst is produced bygamma ray,X-ray, or electron-beam irradiation of clear quartz (rock crystal), which has been first doped with ferric impurities. Exposure to heat partially cancels the irradiation effects and amethyst generally becomes yellow or even green. Much of thecitrine,cairngorm, or yellow quartz of jewelry is said to be merely "burnt amethyst".[1][28]
The Greek wordamethystos may be translated as "not drunken", from Greeka-, "not" +methustos, "intoxicated". Amethyst was considered to be a strong antidote against drunkenness.[a]
In his poem "L'Amethyste, ou les Amours de Bacchus et d'Amethyste" (Amethyst or the loves of Bacchus and Amethyste), the French poetRémy Belleau (1528–1577) invented a myth in whichBacchus, the god of intoxication, of wine, and grapes was pursuing a maiden namedAmethyste, who refused his affections. Amethyste prayed to the gods to remain chaste, a prayer which the chaste goddessDiana answered, transforming her into a white stone. Humbled by Amethyste's desire to remain chaste, Bacchus poured wine over the stone as an offering, dyeing the crystals purple.[b][24](p 58–59)
Variations of the story include that Dionysus had been insulted by a mortal and swore to slay the next mortal who crossed his path, creating fierce tigers to carry out his wrath. The mortal turned out to be a beautiful young woman, Amethystos, who was on her way to pay tribute toArtemis. Her life was spared by Artemis, who transformed the maiden into a statue of pure crystalline quartz to protect her from the brutal claws. Dionysus wept tears of wine in remorse for his action at the sight of the beautiful statue. The god's tears then stained thequartz purple.[34]
This myth and its variations are not found in classical sources. However, the goddessRhea does present Dionysus with an amethyst stone to preserve the wine-drinker's sanity in historical text.[35]
Tibetans consider amethyst sacred to theBuddha and make prayer beads from it.[36][full citation needed] Amethyst is considered thebirthstone of February.[37]In the Middle Ages, it was considered a symbol of royalty and used to decorate English regalia.[37] In theOld World, amethyst was considered one of thecardinal gems, in that it was one of the five gemstones considered precious above all others, until large deposits were found in Brazil.[38]
Until the 18th century, amethyst was included in the cardinal, or most valuable, gemstones (along withdiamond,sapphire,ruby, andemerald), but since the discovery of extensive deposits in locations such as Brazil, it has lost most of its value.[38] It is now considered a semiprecious stone.[39]
Collectors look for depth of color, possibly with red flashes if cut conventionally.[40]As amethyst is readily available in large structures, the value of the gem is not primarily defined by carat weight. This is different from most gemstones, since the carat weight typically exponentially increases the value of the stone. The biggest factor in the value of amethyst is the color displayed.[41]
The highest-grade amethyst (calleddeep Russian) is exceptionally rare. When one is found, its value is dependent on the demand of collectors; however, the highest-grade sapphires or rubies are still orders of magnitude more expensive than amethyst.[7]
The most suitable setting for gem amethyst is aprong or abezel setting. Thechannel method must be used with caution.[42]
Amethyst has a good hardness, and handling it with proper care will prevent any damage to the stone. Amethyst is sensitive to strong heat and may lose or change its colour when exposed to prolonged heat or light. Polishing the stone or cleaning it byultrasonic orsteamer must be done with caution.[42]
An epigram byPlato the Younger also mentions amethyst in connection with drinking: "The stone is an amethyst; but I, the tipler Dionysus, say, "Let it either persuade me to be sober, or let it learn to get drunk."[30]
Pliny says about amethysts: "The falsehoods of the magicians would persuade us that these stones are preventive of inebriety, and that it is from this that they have derived their name."[31] which is why wine goblets were often carved from it.[32]
^The "myth" of Amethyste and Bacchus was invented by the French poetRemy Belleau (1528–1577).[33]
^abcWise, Richard W. (2005).Secrets of the Gem Trade: The connoisseurs' guide to precious gemstones. Lenox, MA: Brunswick House Press.ISBN0-9728223-8-0.
^Belleau, Remy (1576). "L'Amethyste, ou les Amours de Bacchus et d'Amethyste".Les Amours et Nouveaux Eschanges des Pierres Precieuses: Vertus & Proprietez d'icelles [The loves and new transformations of the precious stones: Their virtues and properties] (in French). Paris, FR: Mamert Patisson. pp. 4–6. — Belleau's collection of poems
Kostov, R.I. (1992). Amethyst: A geological-mineralogical and gemmological essay (Report) (in Bulgarian). Sofia, Bulgaria: Union of Scientists in Bulgaria.
Lieber, W. (1994).Amethyst: Geschichte, Eigenschaften, Fundorte. München, DE: Christian Weise Verlag.
