Tuesday, October 12, 2010

amethyst


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Its colour is as unique as it is seductive, though in fact this gemstone of all gemstones is said to protect its wearer against seduction. The amethyst is extravagance in violet. For many thousands of years, the most striking representative of the quartz family has been a jewel coveted by princes both ecclesiastical and secular. Moses described it as a symbol of the Spirit of God in the official robes of the High Priest of the Jews, and the Russian Empress Catherine the Great sent thousands of miners into the Urals to look for it. In popular belief, the amethyst offers protection against drunkenness - for the Greek words 'amethystos' mean 'not intoxicated' in translation. A more apt stone for the month of February, particularly if there is to be plenty going on in the way of carnival celebrations, could thus hardly be wished for.

A large number of further miraculous powers are attributed to the amethyst in all sorts of cultures. It was said to protect crops against tempests and locusts, bring good fortune in war and in the hunt, drive out evil spirits and inspire the intellect. A little study of the works of Pliny will reveal that this gemstone, if worn round the neck on a cord made from dog's hair, affords protection against snakebite. Later, Hieronymus even reported that eagles placed an amethyst in their nest in order to protect their young from the selfsame danger. Apart from these powers, gemstone therapists say that the amethyst has a sobering and cleansing effect. Amethyst has also been said to quell excessive stomach acid and, according to Hildegard von Bingen, served to combat insect bites and beautify the skin. But the amethyst not only had a firm niche in medicine; it was also esteemed as a stone of friendship. And since it was thought to put the wearer in a chaste frame of mind and symbolise trust and piety, the amethyst came to occupy a very prominent position in the ornaments of the Catholic clergy over the centuries. It was the stone of bishops and cardinals; we find it in prelates' crosses and in the so-called Papal Ring (Italian, 15th century) in the Jewellery Museum in Pforzheim.

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However, the most beautiful of all crystal quartzes also posed one or two riddles for the scientists, and indeed they still haven't been completely solved to this day. The amethyst has its hardness (7), its moderate refraction and its weight in common with the other quartzes, but the crystal structure is different, and it is most unconventional. The construction is stratified, as a result of which areas and lamellae of varying colour intensity often come about. This explains why there are relatively few large cut amethysts of an evenly distributed dark colour, in spite of its having been found so abundantly in all parts of the world. It is only in the last few years that scientists have been fairly certain of having found the real cause of the colour. It is now attributed to certain iron constituents in connection with natural radioactive radiation.

One thing that has been known for a long time, on the other hand, is the fact that the amethyst changes its colour on being heated. Smoky stones are transformed at temperatures of as little as 250 degrees to a shining yellow to brownish-red, whilst clear ones, i.e. those with a high degree of transparency, become yellow or colourless at 400 degrees. Now and then Nature gives us a surprise by having created bicoloured stones, like the ones recently found in Bolivia in the form of causticised crystal nuggets. This variety is known as ametrine, for in its formation certain energy states of iron introduce violet areas to the yellow citrine. At best, flat jewellery with a three-spoked star can be cut from it. However, the highlight for esoterics is that the energy fields can in fact be made visible in polarised light. The Henn Brothers of Idar-Oberstein even supply the photos to go with it.

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Some amethysts pale almost to colourlessness in daylight. The reason for this has not yet been discovered, but it is possible to re-colour them by means of radium radiation. The fact that these stones can lose their colour makes it obvious that amethyst jewellery should not be worn while sunbathing, in a solarium or in a discotheque with black light. Sudden changes of temperature can also be harmful to the stone.

The deposits with the greatest economic significance are in various states in southern Brazil and in neighbouring Uruguay. The third major export country is Madagascar. However, this gemstone is spread all over the world. Good specimens were found in Aztec graves, though the deposits from which they were extracted are no longer known today. On the Canadian side of Lake Superior in North America, there is a place named Amethyst Harbor. The violet quartz is found there in ample quantities, though rarely in gemstone quality. The fame of Idar-Oberstein, the German gemstone centre, is based on domestic amethyst finds. In earlier times, raw material was delivered there from the Zillertal Alps. When these nearby deposits ceased to yield, the old cutters' tradition was able to be preserved thanks to supplies organised by German emigrés in South America. Russian amethysts, which were mainly mined in winter in the Urals, were once famous for their particularly beautiful colour, which shone magnificently even in artificial light. In Tibet there were amethyst rosaries, for there the gemstone was dedicated to Buddha and was said to promote clarity of mind. In Sri Lanka, stones which have rolled down on their own are found in debris.

However, the amethyst is more likely to turn up in spaces lining agate almonds and druses in igneous rocks. What was presumed to be the largest-ever cavity was discovered in 1900 in Rio Grande do Sul. The almond measured ten by five by three metres (33 by 16 by 10 ft.) and weighed an estimated eight tonnes. The dark violet amethysts, some as large as a man's fist, may have weighed some 700 cwt. altogether. There is a piece weighing 200 kilogrammes, taken from this Brazilian treasure, in the Washington Museum. In recent times, a find in the USA has been making headlines. In July 1993, a three-metre druse was found in Maine, which contained well over 1000 kilogrammes of cuttable amethyst, some of it in crystals 19 cm in length.

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The South American deposits in particular, which were not discovered until the nineteenth century, brought down the price of the violet gemstone. The amethyst bracelet of Queen Charlotte of England, which was so famous at the beginning of the 18th century, its value being estimated at 2000 pounds sterling at that time, was apparently worth only 100 pounds 200 years later. However, the price has a close relationship with the quality, and the quality varies immensely. Most of the material from Brazil is light-coloured, a tender purple. In Madagascar, it is generally red or violet hues which are found. Uruguay supplies the most beautiful and the deepest colour, but it is mostly blemished. Thus immaculate stones of the finest violet still fetch carat prices of well over a hundred euros. Mounted with diamond braid trimming, as has been the custom for some 100 years, enchanting pieces of jewellery are thus created. No wonder that people find it worth going to the trouble of producing imitations and synthetics.

In ancient times, amethyst was already being engraved and cut into sculptured forms, witness the bust of Trajan which Napoleon captured in Berlin. Amethyst quartz, banded with whitish layers, is particularly good to work with, though it is only ever either translucent or opaque or somewhere in between. In earlier times, people liked to drink wine from amethyst cups, which brings us back to the stone's protective function against alcoholism. According to the ancient Greek saga, Diana turned a nymph whom Bacchus loved into an amethyst; hence the term Bacchus stone. Anyone wishing to protect a drunkard from delirium mixed some pulverised amethyst into the person's drink.



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Amethyst is a violet variety of quartz often used in jewelry. The name comes from the Ancient Greek ἀ a- ("not") and μέθυστος methustos ("intoxicated"), a reference to the belief that the stone protected its owner from drunkenness; the ancient Greeks and Romans wore amethyst and made drinking vessels of it in the belief that it would prevent intoxication.


Chemistry
Amethyst is the violet variety of quartz; its chemical formula is SiO2.

In the 19th century, the color of amethyst was attributed to the presence of manganese. However, since it is capable of being greatly altered and even discharged by heat, the color was believed by some authorities to be from an organic source. Ferric thiocyanate was suggested, and sulfur was said to have been detected in the mineral.

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More recent work has shown that amethyst's coloration is due to ferric iron impurities.
 Further study has shown a complex interplay of iron and aluminium is responsible for the color.
On exposure to heat, amethyst generally becomes yellow, and much of the citrine, cairngorm, or yellow quartz of jewelry is said to be merely "burnt amethyst". Veins of amethystine quartz are apt to lose their color on the exposed outcrop.

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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 gemological testing (which is often cost-prohibitive). There is one test based on "Brazil law twinning" (a form of quartz twinning where right and left hand quartz structures are combined in a single crystal) which can be used to identify synthetic amethyst rather easily. In theory however it is possible to create this material synthetically as well, but this type is not available in large quantities in the market.
Amethyst is composed of an irregular superposition of alternate lamellae of right-handed and left-handed quartz. It has been shown that this structure may be due to mechanical stresses.
Because it has a hardness of seven on the Mohs scale, amethyst is suitable for use in jewelry.



History

Amethyst was used as a gemstone by the ancient Egyptians and was largely employed in antiquity for intaglio engraved gems.
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The Greeks believed amethyst gems could prevent intoxication, while medieval European soldiers wore amethyst amulets as protection in battle – the reason for this being that amethysts are believed to heal people and keep them cool-headed. Beads of amethyst were found in Anglo-Saxon graves in England.

A large geode, or "amethyst-grotto", from near Santa Cruz in southern Brazil was presented at the 1902 exhibition in Düsseldorf, Germany.
Amethyst is the traditional birthstone for February.
The Greek word "amethystos" may be translated as "not drunken", from Greek a-, not + methustos, intoxicated. Amethyst was considered to be a strong antidote against drunkenness, which is why wine goblets were often carved from it. In Greek mythology, Dionysus, the god of intoxication, and of wine, was pursuing a maiden named Amethystos, who refused his affections. Amethystos prayed to the gods to remain chaste, a prayer which the goddess Artemis answered, transforming her into a white stone. Humbled by Amethystos's desire to remain chaste, Dionysus poured wine over the stone as an offering, dyeing the crystals purple.



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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. Another variation involves the titan Rhea presenting Dionysus with the amethyst stone to preserve the wine-drinker's sanity.


Geographic distribution

Amethyst is produced in abundance from the state of Minas Gerais in Brazil where it occurs in large geodes within volcanic rocks. Many of the hollow agates of southwestern Brazil and Uruguay contain a crop of amethyst crystals in the interior. Artigas, Uruguay and neighboring Brazilian state Rio Grande do Sul are large world producers exceeding in quantity Minas Gerais, as well as Mato Grosso, Espirito Santo, Bahia, and Ceará states, all amethyst producers of importance in Brazil.

It is also found and mined in South Korea. The largest opencast amethyst vein in the world is in Maissau, Lower Austria. Much fine amethyst comes from Russia, especially from near Mursinka in the Ekaterinburg district, where it occurs in drusy cavities in granitic rocks. Many localities in south India yield amethyst. One of the largest global amethyst producers is Zambia in southern Africa with an annual production of about 1000 tonnes.
Amethyst occurs at many localities in the United States. Among these may be mentioned: the Mazatzal Mountain region in Gila and Maricopa Counties, Arizona; Amethyst Mountain, Texas; Yellowstone National Park; Delaware County, Pennsylvania; Haywood County, North Carolina; Deer Hill and Stow, Maine and in the Lake Superior region of Minnesota, Wisconsin, Michigan, and Ontario in Canada. Amethyst is relatively common in Ontario, and in various locations throughout Nova Scotia. The largest amethyst mine in North America is located in Thunder Bay, Ontario.
Up to the 18th century, amethyst was included in the cardinal, or most valuable, gemstones (along with diamond, sapphire, ruby, and emerald). 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.The highest grade amethyst (called "Deep Russian") is exceptionally rare and therefore its value is dependent on the demand of collectors when one is found. It is however still orders of magnitude lower than the highest grade sapphires or rubies (padparadscha sapphire or "pigeon's blood" ruby).


 
From Wikipedia, the free encyclopedia