Amethyst is a violet variety of quartz often used in jewelry. The name comes from the ancient Greek ἀ a- and μέθυστος méthystos, a reference to the belief that the stone protected its owner from drunkenness. The ancient Greeks wore amethyst and made drinking vessels decorated with it in the belief that it would prevent intoxication. It is one of several forms of quartz. Amethyst is a semiprecious stone and is the traditional birthstone for February.
Amethyst is a purple variety of quartz and owes its violet color to irradiation, iron impurities, and the presence of trace elements, which result in complex crystal lattice substitutions. The hardness of the mineral is the same as quartz, thus it is suitable for use in jewelry.
Hue and tone
Amethyst occurs in primary hues from a light pinkish violet to a deep purple. Amethyst may exhibit one or both secondary hues, red and blue. The best varieties of amethyst can be found in Siberia, Sri Lanka, Brazil and the far East. The ideal grade is called “Deep Siberian” and has a primary purple hue of around 75–80%, with 15–20% blue and red secondary hues. Green quartz is sometimes incorrectly called green amethyst, which is a misnomer and not an appropriate name for the material, the proper terminology being prasiolite. Other names for green quartz are vermarine or lime citrine.
Of very variable intensity, the color of amethyst is often laid out in stripes parallel to the final faces of the crystal. One aspect in the art of lapidary involves correctly cutting the stone to place the color in a way that makes the tone of the finished gem homogeneous. Often, the fact that sometimes only a thin surface layer of violet color is present in the stone or that the color is not homogeneous makes for a difficult cutting.
The color of amethyst has been demonstrated to result from substitution by irradiation of trivalent iron for silicon in the structure, in the presence of trace elements of large ionic radius, but loses its dichroism, unlike genuine citrine. When partially heated, amethyst can result in ametrine.
Amethyst can fade in tone if overexposed to light sources and can be artificially darkened with adequate irradiation.
The Greeks believed amethyst gems could prevent intoxication, while medieval European soldiers wore amethyst amulets as protection in battle in the belief that amethysts heal people and keep them cool-headed. Beads of amethyst were found in Anglo-Saxon graves in England. Western Christian bishops wear an episcopal ring often set with an amethyst, an allusion to the description of the Apostles as “not drunk” at Pentecost in Acts 2:15.
A large geode, or “amethyst-grotto”, from near Santa Cruz in southern Brazil was presented at a 1902 exhibition in Düsseldorf, Germany.
In the 19th century, the color of amethyst was attributed to the presence of manganese. However, since it can be greatly altered and even discharged by heat, the color was believed by some authorities to be from an organic source. Ferric thiocyanate has been suggested, and sulfur was said to have been detected in the mineral.
Synthetic amethyst is produced by gamma ray, X-ray or electron beam irradiation of clear quartz which has been first doped with ferric impurities. On exposure to heat, the irradiation effects can be partially cancelled and amethyst generally becomes yellow or even green, and much of the citrine, cairngorm, or yellow quartz of jewelry is said to be merely “burnt amethyst”.
Synthetic amethyst is made to imitate the best quality amethyst. Its chemical and physical properties are so similar to that of natural amethyst that it can not be differentiated with absolute certainty without advanced gemnological testing . There is one test based on “Brazil law twinning” which can be used to identify synthetic amethyst rather easily. It is possible to synthesize twinned amethyst, but this type is not available in large quantities in the market. Amethyst was considered to be a strong antidote against drunkenness, which is why wine goblets were often carved from it. In his poem “L’Amethyste, ou les Amours de Bacchus et d’Amethyste”, the French poet Remy Belleau invented a myth in which Bacchus, the god of intoxication, of wine, and grapes was pursuing a maiden named Amethyste, who refused his affections. Amethyste prayed to the gods to remain chaste, a prayer which the chaste goddess Diana 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.
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 to Artemis. 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 the quartz purple.
This myth and its variations are not found in classical sources. Although the titan Rhea does present Dionysus with an amethyst stone to preserve the wine-drinker’s sanity in historical text.
Other cultural associations
Tibetans consider amethyst sacred to the Buddha and make prayer beads from it. Amethyst is considered the birthstone of February. In the Middle Ages, it was considered a symbol of royalty and used to decorate English regalia.
Up until the 18th century, amethyst was included in the cardinal, or most valuable, gemstones . However, since the discovery of extensive deposits in locations such as Brazil, it has lost most of its value.
Collectors look for depth of color, possibly with red flashes if cut conventionally. As amethyst is readily available in large structures the value of the gem is not primarily defined by carat weight; this is different to most gemstones where the carat weight exponentially increases the value of the stone. The biggest factor in the value of amethyst is the color displayed.
The highest grade amethyst is exceptionally rare and therefore, when one is found, its value is dependent on the demand of collectors. It is, however, still orders of magnitude lower than the highest grade sapphires or rubies .
List of minerals