Amethyst

 

amethyst the purple variety of the mineral quartz

 

Amethyst is an alluring and popular variety of the mineral quartz which is relatively easy to identify. It occurs in colours ranging from purple to violet which are caused primarily by the presence of iron, the specific shade and intensity of colour however, is determined by impurities of manganese. Heat and pressure also play a part but natural minerals are formed through a variety of different processes so should one change or not be present, the outcome may well be the formation of a different stone.

The colour within a single amethyst crystal is often unevenly distributed and when heated, the amount of iron that's present is gradually reduced. By interfering with its chemical make-up, amethyst begins to change colour. Heat treatments mimic natural geological processes and can be used to remove unwanted tinges of colour, to lighten or darken a gemstone or to change its colour completely. Much of the citrine that's available to buy is actually heated amethyst because natural citrine is rare hence it can be quite expensive. When heated to around 450°C (842°F) amethyst starts to turn yellow and as the temperature is further increased, it changes to rich orange and then orange-brown. Temperature and the duration of a heat treatment will determine the final colour of the stone. Ametrine is a rare mineral that's a combination of purple and yellow quartz and while it does occur naturally, most of the world's supply comes from one mine in Bolivia although smaller amounts can also been found in India and Brazil. Like citrine, ametrine can also be produced artificially through various heat treatments.

four faceted citrine gemstones Faceted citrine gemstones (heated amethyst)


Enhancing and changing the colour of rocks, minerals and gemstones through the application of heat is almost as old as the gem trade itself. Theophrastus the ancient Greek philosopher (c.370 - 285 BC) documented in his treatise Theophrastus On Stones, "amethyst loses its colour in the fire like the sapphire and emerald" and subsequently Pliny the Elder [23 - 79 AD] Ancient Roman author, naturalist and philosopher talks about "giving quartz the colour of emeralds" and "how to change one gemstone into another".

The earliest reference to amethyst can be traced back over 5000 years to 3100 BC and it's known to have been a popular and highly sought after gemstone in Ancient Egypt. Theophrastus writes that it's wine coloured and along with rock crystal can be found by "dividing other stones", he says both are often found in veins, cavities or lining the interior of geodes and are only revealed when rocks are broken open. The first English translation of Theophrastus' History of Stones (Theophrastus On Stones) by the author and botanist John Hill was published in 1746 and in it he says

"Although the ancients" knew of five species of amethyst, we have at least as many among the jewellers at present, though they are not at the pains to distinguish them by particular names, they divide them in general into Οriental and Occidental. The former are very fierce but of great hardness, lustre and beauty, the latter are had from many places particularly Saxony, Germany and Βοhemia".

It's believed that in the past translucent gemstones of a similar colour were grouped together so amethyst would have been in the same group as fluorite, corundum (blue and violet corundum is better known as sapphire) and possibly even tourmaline. Oriental Amethyst was a reference to stones which came from the East and "occidental" means "relating to the West".

Later writers like Pliny also compare the colour of amethyst to wine and in his works Naturalis Historia (Natural History) he writes,

"We will now commence with another class of precious stones, those of a purple colour or whose tints are derived from purple. To the first rank belongs the amethystos".

He says,

"All of these stones are transparent and of an agreeable violet colour and easy to engrave, those of India have in perfection the very richest shades of purple and it is to attain this colour that the dyers in purple direct all their endeavours"

This is where things become a little confusing and we're totally reliant on various translations of the original text to work out exactly which gemstones Pliny is referring to.  Corundum would not have been easy to engrave because it's very hard and sits just under diamond on Mohs scale of mineral hardness so it's generally believed it was not included in the rank of amethystos. This is supported by his descriptions of these gemstones in which he says, "they have a fine mellowed appearance to the eye and not dazzling the sight like the colours of the carbunculas" (garnet). He goes on to say "the colour of one is almost hyacinth whilst another borders on crystal with the purple gradually passing off into white". Of the latter he says it has little value because when viewed sideways and held up to the light, fine amethyst (a reference to corundum) should always have a purple brilliance like that of the carbunculus "slightly inclining to a tint of rose".

He states that the name amethystos according to "some authorities" comes from the Ancient Greek words for "not" and "to intoxicate" on account that it's "a supposed preservative against inebriety" and it's believed with this statement that Pliny is not referring solely to the rank of stones known as amethystos, but to the entire class of precious stones which are purple or whose tints are derived from purple which includes corundum, fluorite and possibly garnet amongst others.

In another paragraph he talks about how amber is used to counterfeit certain gemstones and says,

"Amber too is greatly in request for the imitation of the transparent precious stones, amethystos in particular for as already stated, it admits of being dyed of every colour"



upright standing purple coloured amethyst geode and to its right a purple coloured sapphire
Amethyst geode, faceted purple sapphire (corundum)

 

In 1846 John Kitto published an encyclopaedia called "A Cyclopaedia of Biblical Literature" in which he talks about how the Ancient Egyptians counterfeited precious stones. He writes that glass was known and made by these "ingenious people at a very early period", glass ornaments were made about 1500 years B.C and glass vases were used for holding wine as early as the Exodus. He says "such was the skill of the Egyptians in this manufacture that they successfully counterfeited the amethyst and many other precious stones". The following excerpt demonstrates how the word amethyst in ancient writings did not just refer to the purple variety of quartz,

"The transparent gems to which this name is applied are of a colour which seems composed of a strong blue and deep red and according as either of these prevails, exhibit different tinges of purple sometimes approaching to violet and sometimes declining even to a rose colour. From these differences of colour the ancients distinguished five species of amethyst, modern collections afford at least as many varieties but they are all comprehended under two species, the oriental amethyst and the occidental amethyst. These names, however are given to stones of essentially different natures which were no doubt, anciently confounded in the same manner. The oriental amethyst is very scarce and of great hardness, lustre and beauty. It is in fact a rare variety of the adamantine spar or corundum. Next to diamond it is the hardest substance known. To this species also belongs the sapphire, the most valuable of gems next to the diamond and of which the oriental amethyst is merely a violet variety. Like other sapphires it loses its colour in the fire. The more common or occidental amethyst is a variety of quartz or rock crystal and is found in various forms in many parts of the world as India, Siberia, Sweden, Germany, Spain and even in England very beautiful specimens of tolerable hardness have been discovered. This also loses its colour in the fire. Amethysts were much used by the ancients for rings and cameos and the reason given by Pliny, was because they were easily cut."

amethyst smithsonian

Amethyst exhibits in the Smithsonian Institute, Washington D.C | Photo: Stone Mania ©

 

During biblical times amethyst is believed to have been the third stone in the third row of the high priest's breastplate or Breastplate of Aaron, a religious garment worn by the Jewish high priest. It was adorned with twelve precious gemstones each of which had the name of one of the twelve tribes of Israel inscribed onto it. In the Middle Ages amethyst was believed to encourage celibacy and symbolize piety (dutiful devotion to God and observance of religious principles) hence it was a favourite of the church and more recently, it can be seen in the Royal Sceptre which is part of the British Crown Jewels.  This item which is crafted entirely from gold features a huge purple gemstone mounted below a diamond encrusted cross with an emerald in the centre and also features the Cullinan I which is the world's largest clear cut diamond.

Many articles that have been written about amethyst make reference to a story from Greek mythology which is supposed to explain how the name came about but despite extensive research over many years, we have never been able to find any hard evidence to support its existence. The only known reference to amethyst relates to a stone that was given to Dionysus (Greek God of wine) by the titan Rhea in order to preserve the wine-drinker's sanity.

In 1576 however which is a long time after the fall of Ancient Greece, a book of poems was published that had been written by a French poet by the name of Remy Belleau and one bore a striking resemblance to this apparent Greek myth. Published less than ten months before his death, there is nothing to suggest it was based on any original text from Greek mythology. Bacchus is the name adopted by the Romans for Dionysus, Greek God of wine.

"Bacchus was pursuing a maiden named Amethyste who refused his affections. Amethyste prayed to the gods to remain chaste, a prayer which the 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"

Amethyst which is the birthstone for the month of February can be found in several countries around the world but some of the finest specimens come from Africa and South America. Rough and polished stones are keenly sought after by collectors, crystals are popular for use in alternative therapies such as crystal healing and polished gemstones may either be cut as a cabochon or faceted. Its colour is delicate and will fade over time if exposed to bright light for long periods of time which is worth bearing in mind when looking for a suitable position to place a piece of amethyst.

a polished amethyst point between two sets of amethyst tumbled stones Amethyst tumbled stonesametrine pointbanded (chevron) amethyst tumbles


Banded or chevron amethyst (the latter being a more American term) is a combination of amethyst and milky quartz, it's a distinctive mineral that's sometimes mistaken for rare Derbyshire Blue John which is a variety of fluorite. Prasiolite is a type of green quartz which occurs very rarely in nature and the vast majority is produced by heat treating amethyst. It is sometimes referred to as green amethyst which is wholly inaccurate and a misnomer because amethyst is the geological name for the purple variety of quartz.



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Further Reading:
Mindat - Amethyst
Amethyst from Wikipedia

 

 

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