Opals
All of Nature’s splendour seems to be reflected in the manifold opulence of fine Opals: fire and lightnings, all the colours of the rainbow and the soft shine of far seas. Australia is the classical country of origin. Almost ninety-five per cent of all fine opals come from the dry and remote outback deserts.
Numerous legends and tales surround this colourful gemstone, which can be traced back in its origins to a time long before our memory, to the ancient dream time of the Australian aborigines. It is reported in their legends that the creator came down to Earth on a rainbow, in order to bring the message of peace to all the humans. And at the very spot, where his foot touched the ground, the stones became alive and started sparkling in all the colours of the rainbow. That was the birth of the Opals.
The group of fine Opals includes quite a number of wonderful gemstones, which share one characteristic: they shine and sparkle in a continually changing play of colours full of fantasy, which experts describe as “opalising”. Depending on the kind, place of occurrence, and colour of the main body, we differentiate Dark or Black Opal, White or Light Opal, Milk or Crystal Opal, Boulder Opal, Opal Matrix, Yowah Nuts from Queensland – the so-called “picture stones“, and also Mexican and Fire Opal. Opal variations are practically unlimited. They all show in their own special way that unique play of colours – except for Fire Opal, which due to its transparency, however, is nevertheless also considered a Fine Opal specimen. If Opals are lacking the typical play of colours, they are simply named “Common Opal”.
Upala, opallios or Opalus – fascination created by tiny spheres
The name Opal was probably derived from Sanskrit “upala“, meaning ”valuable stone“. This was probably the root for the Greek term “opallios”, which translates as “colour change”. In the days of Roman antiquity there existed a so-called “opalus”, or a “stone from several elements”. So the ancient Romans may already have had an inkling why the Opals show such a striking play of colours. But we will come to this later …
Pliny, the famous Roman author, called Opal a gemstone which combines the best possible characteristics of the most beautiful of gemstones: the fine sparkle of Almandine, the shining purple of Amethyst, the golden yellow of Topaz, and the deep blue of Sapphire, ”so that all colours shine and sparkle together in a beautiful combination“.
Up to the first half of the 19th century, Opals were relatively rare. But then their career boomed suddenly and made them one of the most popular gemstones, and the start of this development brought them to the gemstone cutters of the gemstone centre of Idar-Oberstein. In the era of Art Deco the Opals experienced their flourishing, with contemporary gemstone artists preferring them to all other stones because of their subdued charm, which in turn was excellently suited to be combined with enamel, another very popular material of those days.
Opal’s colour play emanates a very special attraction and fascination. But what causes this phenomenon? This question was impossible to answer for a very long time. Only when in the 1960s a team of Australian scientists analysed Opals with an electron microscope, it was discovered that small spheres from silica gel caused interference and refraction manifestations, which are responsible for the fantastic play of colours. The spheres, which are arranged in more or less compact structures, succeed in dissecting the light on its passage through the gemstone and turning it into all the colours of the rainbow, always new and always different.
Australia, classical Opal country
Australia is the classical Opal country and today is the worldwide most important supplier of Fine Opals. Almost 95 per cent of all Opals come from Australian mines. The remaining five per cent are mined in Mexico, and in Brazil’s north, also in the US states of Idaho and Nevada, but recently the stones have also been found in Ethiopia and in the West African country of Mali.
The history of Australian Opal began actually millions of years ago, when parts of Australia were covered by a vast inland sea, and stone sediment was deposited along its shoreline. When the water masses flooded back, they flushed water containing silica into the resulting cavities and niches in the sedimentary rocks, and also the remains of plants and animals were deposited there. Slowly the silica stone transformed into Opal, for basically Opals are simply a combination of silica and water. Or, to be more precise: Opals are a gel from silica, with varying percentages of water.
In 1849 the first Opal blocks were accidentally found on an Australian cattle station called Tarravilla. The first Opal prospectors started in 1890 at White Cliff mining the Opal rocks. And even today the eyes of Opal lovers light up when somebody mentions places like White Cliffs, Lightning Ridge, Andamooka or Coober Peddy: for these are the legendary sites of the Australian Opal fields. The most famous one is probably Lightning Ridge, the place where mainly the coveted Black Opal is found. Andamooka, where Crystal Opal and Light Opal are brought to the light of day, cam boasts to be the place where the probably largest Opal was found, with a weight of 6,843 kilograms, the “Andamooka Desert Flame”. Coober Peddy, by the way, is a word from Aborigine language meaning „white man in a hole“. This clearly describes how Opal was in fact mined: many Opal prospectors made their home in deep holes or caves in the ground, to protect themselves from the burning heat of daytime and from the icy winds of night time. Usually they worked only with tolls such as pick and shovel. Buckets full of soil, hopefully containing Opal rocks, were pulled up out of the depths of 5 to 40 m deep shafts by hand, for this is the depth of the Opal containing crevices and cavities, which are also mined nowadays.
Being an Opal prospector is still not an easy job, although today of course there are some technical means available, such as trucks or conveyor belts. And still the hope to make the find of a lifetime which will let you live happily ever after attracts many men and women to come to the hot and dusty Australian outback.
About cabochons, doublets and triplets
In order to best bring out the play of colour in a Fine Opal, the stones are cut and polished to round or oval cabochons, or any other softly domed shape, depending on the raw material. Only the best qualities of Fire Opal, however, are suited to faceting. The Opal cutter will first of all carefully remove any impurities using a diamond cutting wheel, before working out the rough basic shape. The comes the fine cutting, the finishing with sandpaper and then the final polishing with a wet leather wheel.
Opal is often found as flat lenses, or thin layers, bigger pieces are rather rare. If you leave a thin but supporting layer of the harder mother rock, you will receive a pre-stage of the Opal-doublets which are frequently used today for mass produced jewellery. These are gemstone combinations consisting of a surface from millimetre-thin Opal plates, which have been mounted on Onyx, Obsidian, artificial black glass, or Potch-Opal. Triplets have been developed from this design; here the Opal layer receives an additional cover from Rock Crystal, Plastic, Hard Glass or Lead Glass for protection.
Opal love to be worn on the skin
Due to the differing percentage of water, Opals may easily become brittle. They always contain water – usually between 2 and 6 per cent, but sometimes even more. Thus if stored too dry or exposed to heat over a longer period of time, Opals will show fissures and the play of colour will become paler. Therefore, Opal jewellery should be worn as often as possible, for then the gemstone will receive the needed humidity from the air and from the skin of its wearer.
Opals are not very hard: they only achieve 5.5 to 6 on the Mohs’ scale. Therefore they appreciate a protective setting. In earlier days Opal’s sensitive surface was often oiled, but today also sealing them with colourless artificial resin has become quite popular.
From Harlequin to Peacock: Opal experts lingo
When Opal experts talk about “harlequin”, “church windows” or “needle fire”, do not be surprised. They are probably discussing Opals. The play of colour in this stone is described with many imaginative terms for various structures and phenomena, like, for example, “flame opal”, “lightning and peacock opal”, or the above named “harlequin” and “church window”.
Opal’s value is not only determined by the body colour, transparency and factors based on place of occurrence. (Body colour refers to the basic colour of the gemstone, which can be black, dark or light and coloured). It is also important if the stone is transparent, translucent or opaque. And the opalizing effect may also influence the transparency.
Black Opal or Opal with a dark grey body shows the most brilliant play of colours imaginable. Crystal opal, which comes immediately after Black Opal in the hit list, should be more transparent with a deep play of colours. White or milky Opals show more diffuse colours and are the least expensive Opals. The occurrence-specific characteristics include, for instance, denominations such as “Black Opal from Lightning Ridge” (we are talking absolute top luxury here) or “Mexican Fire Opal”.
The most important criterion for determining the price of an Opal, however, is the play of colour, the colours as such and their pattern. If the colour red appears when looking through the stone, all the other colours will appear also. For evaluating Opals the thickness of the Opal layer is considered, the beauty of the patterning, the cut, weight and finish. Finally the total impression will be decisive, and of course offer and demand will determine ho much you will have to pay for “your” Opal. If you are interested in a really valuable specimen, get an Opal expert to advise you, because it takes a real expert to know about the many criteria which determine the price.
Opals and emotions
For ages people have been believing in the healing power of Opal. It is reported to be able to solve depressions and to help its wearer find the true and real love. Opals are supposed to further enhance the positive characteristics for people born under the zodiac sign of Cancer. Black Opal is recommended to those born under Scorpio, and Boulder Opal is the lucky stone for Aries.
The fantastic colour play of Opal reflects changing emotions and moods of people. Fire and water, the sparkling images of Boulder Opal, the vivid light flashes of Black Opal or the soft shine of Milk Opal – striking contrasts characterise the colourful world of this fascinating gemstone. Maybe this is the reason why it depends on our daily mood which Opal we prefer. Opals are like human emotions: you always experience them different and anew.
Legends and lore
Historically, Opal was considered a lucky charm that brought beauty, success and happiness to its wearer. The early Greeks believed Opals embodied the powers of foresight and prophecy.
The Romans also cherished Opals, considering them to be a symbol of hope and purity - an appropriate attribute for a gem with a rainbow locked within it!
The Arabs thought that Opals must have fallen from heaven in flashes of lightning. According to Arab tradition, it is believed that Opals prevent lightening strikes, shield its wearer from any undesirable elements in their day-to-day lives and give a cloak of invisibility to its wearer when desired.
Opal featured in literature with Shakespeare referring to it in “Twelfth Night” as “the queen of gems.”
The history books would have us believe that the European supplies of Opal came from India and the Middle East, but it is far more likely that they came from Hungarian mines.
Opal made the headlines in the 1890’s with the first samples of Australian Opal. The Hungarians declared that the new Australian variety was not the real thing, as Opals with such a fusion of fire and color had never been seen before. According to Koori (indigenous Australians) legend, the Creator came down to earth on a rainbow to bring a message of peace to all humans. At the spot where his feet touched the ground, the stones became alive and started sparkling in all the colors of the rainbow, giving birth to Australian Opals. Today, Opals are one of Australia’s national treasures and one of the world’s most prized gemstones.
Queen Victoria intervened in the near destruction of the 19th century Opal market when the writer Sir Walter Scott started a superstition that Opals were bad luck for people not born in October. In one of his novels, the heroine owned an Opal that burned fiery red when she was angry and turned ashen gray upon her death. Queen Victoria finally dispelled the curse by giving Opal jewelry as gifts at a royal wedding.
Scandinavian women still wear Opal hair bands to ward off the onset of gray hair, while some people believe that this gemstone has therapeutic properties that rejuvenate the inner spirit and invigorate the mind.
Just the facts
Opals possess flashes of rainbow colours that change with the angle of observation, called “play of colour.” This effect is similar to the rainbow colors displayed on a soap bubble, only much more dramatic. This should not be confused with “opalescence,” which is the milky blue or pearly appearance of Opal caused by the reflection of light.
The physical structure of Opal is unique. Tiny precipitated spheres of silicon dioxide form a pyramid shaped grid interspersed with water. Tiny natural faults in this grid cause the characteristic play of colour.
Opals are typically classified depending on the “potch” (the host rock, also called the “matrix”) on which the Opal is formed and their resulting transparency. For example, Black Opal has a black potch, Semi Black Opal has a potch darker than gray, but not quite black, White Opal has a white potch, Queensland Boulder Opal is Opal with an ironstone (boulder) potch and Jelly Opal (also know as Crystal Opal) is Opal with no potch whatsoever. Distinguished from Jelly Opal by its minimal play of colour, Fire Opal is Jelly Opal that displays extraordinary fiery yellows, tangerines and reds. Matrix Opal (also know as “opal with matrix”) are any Opals where the potch or matrix is visible face up.
Opal actually exhibits many different colours including cherry coloured specimens that rival Ruby, fiery-orange Opals that sparkle like Spessartite Garnet, tropical blue gems as intense as Chalcedony, and even gorgeous pinks and greens.
Today approximately 95% of the world’s Opal is sourced from a handful of prominent mining areas in Australia, namely Lightning Ridge, Coober Pedy, Andamooka and Mintabe.
Black Opal
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Black Opal is principally found at Lightning Ridge in New South Wales, Australia. Known as the “King of Opals,” Lightning Ridge Black Opal has been coveted since it was discovered in 1902. Located 575 miles north of Sydney, Lightning Ridge (a free wheeling town of about 15,000 people) is the world’s major source of the finest Black Opal.
This magnificent gemstone is the most coveted form of Opal. Its dark background colour sets the spectral colours ablaze much like a storm cloud behind a rainbow (the black background provides contrast and intensity to this Opal’s play of colour). So prized is Black Opal that even wafer thin slices are made into doublets or triplets to give them enough strength and depth to set into gold rings and other jewellery items.
The Black Opal mining fields of Lightning Ridge and the majority of Australia’s Opal fields are located in a geological phenomenon called “The Great Australian Basin.” The basin was formed from sediments of a large inland sea that existed over 140 million years ago. Approximately 120 million years later, sandstones were deposited by waterways over the top of these sedimentary rocks. Eventually these younger rocks weathered, and their silica filtered down to cavities in the older host rock in the form of a gel. The silica gel hardened forming around a nucleus, creating the Opal’s characteristic regular spheres and voids. It’s the diffraction of light through these transparent spaces that produce Opal’s brilliant play of colours.
Mined directly from narrow seams in sedimentary rock, Opal mining involves hard digging with picks and shovels 20-59 feet underground. Buckets are then loaded and hauled to the surface using simple mechanical winches. The rough Opal (called “nobbies”) is initially separated by hand, prior to sieving. The remaining Opal nobbies are then taken to small converted cement mixers to wash off the excess dirt.
Unfortunately, all Australian Opal, but especially those from Lightning Ridge, are becoming increasingly scarce. The old fields at Lightning Ridge that produced high dome cabochons are virtually depleted, with only marginal areas presently being worked. Despite the fact that the government has opened many new prospective areas, to date there have been no significant new prospects found. Opal production at Lightning Ridge is half of what it was 10 years ago. The current supply problems are infuriating as international demand remains high. The present jewellery trends favouring colour have seen an increase in Opal use among the world’s leading jewellery houses.
Boulder Opal
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Boulder Opal is found sparsely distributed over a wide area of Australian ironstone or boulder country where the Opal (silica mix) fills veins, cracks, cavities and crevices in ironstone boulders. Opal bearing boulder is always cut to include the host brown ironstone. The GIA (Gemmological Institute of America) classifies two types: gems with ironstone visible face up, called “opal with matrix” and gems with no visible inclusions, called “opal in matrix.” Boulder Opal is usually cut as “opal with matrix” to the contours of the Opal vein, creating a baroque wavy surface often freeform and irregular in shape, making each Boulder Opal unique. Located northwest of Lightning Ridge in western Queensland, the Queensland Boulder Opal Fields encompass a vast area centering on the town of Quilpie and extending as far north as Winton and south to Cunamulla. The last 12 months have seen slightly lower production levels, with any fine gems quickly snapped up. Known for its lively flaming bright rich colours, this variety is in very high demand and extremely popular. Interest in Queensland Boulder Opal has increased markedly over the last 20 years as this unique type of Opal gains recognition from gem enthusiasts the world over.
Fire Opal
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Fire Opals are appropriately named for their fiery cherries, sunburst yellows and deep tangerines. Unique and mysterious, Fire Opal is remarkable in that unlike many other Opals its play of colour is minimal. Also known as Mexican Opal, Mexican Fire Opal, Tanzanian Fire Opal, Cherry Fire Opal, Ethiopian Fire Opal, Brazilian Fire Opal or Sun Opal, its legendary popularity instead comes from its breathtaking brilliance, opalescence, extraordinary fiery hues and stunning clarity. Fire Opals have been treasured in the Americas since the time of the Aztecs, where they were named “quetzalitzlipyollitli” or “gemstone of the bird of paradise.” Coveted by the Aztecs as symbols of intense love, such radiant gemstones were believed to have emerged from the primordial waters of creation.
While Fire Opal is predominately sourced from Mexico (and occasionally Australia), this gem has recently been found in Tanzania, Ethiopia, Mali and now Brazil. While Opal has been mined in Brazil since approximately 1945, production has always been very limited, making it difficult to secure commercial quantities. Today, the Piaui State is increasingly garnering international acclaim for its Opals, with their quality favourably compared to Australian Opals, arguably the worlds finest. With the enforcement of new mining regulations, scarcity has increased, strengthening the appeal of this relatively new addition to the Opal family.
Green Opal
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Discovered in the 1960’s, Green Opal is a green translucent Opal that resembles Chrysoprase or Jade and is commonly called Prase Opal or Chrysopal because of its resemblance to Chrysoprase. It is mined in the Arusha region of Tanzania (the same region as Tanzanite). While this gem does not display the play of colour found in some Opals, its mint to apple green body colour has made it very popular for jewellery. Trace amounts of nickel gives this Opal its unique colour.
Jelly Opal
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Jelly Opal (also known as Water Opal or Crystal Opal) is mined in Mexico and Australia. Offering an attractive blend of indistinct colours, it is transparent pure Opal with a gelatinous appearance and an occasionally pronounced opalescence (bluish sheen). The play of colour is a subtle sheen dancing throughout the gem, rather than distinct colour patches. When held out in direct light, Jelly Opal can display some of the most intense Opal colours. Very occasionally it is also found in Lightning Ridge, Australia, where it is essentially Black Opal without the black potch background. This is the type of Opal used in Opal inlay jewellery that has the base of the setting blackened (typically using black rhodium) before a precisely cut crystal Opal is set within.
Peruvian Opal
Hailing from the Andes and coveted by the ancient Incas, Peruvian Opal is extremely rare and exhibits an exquisite translucent colouring. While it typically comes in blue or pink colours, greens are also occasionally found.
Semi Black Opal
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With a brighter transparency than Black Opal, Semi Black Opal has a body colour darker than gray, but not quite black. Opacity is the key that divides black from semi black with Black Opal appearing more opaque than Semi Black Opal. Semi Black Opal was discovered at Andamooka in the 1930’s. Situated 398 miles north by road from Adelaide, South Australia, Andamooka remains a typical dusty “wild west” desert town. In the 1960’s when Andamooka was booming, an Opal setting (at the time worth hundreds of thousands of dollars) was presented to Queen Elizabeth II. While Andamooka Opals remain world renowned, only a small amount of Opal is now mined from Andamooka due to high logistical expenses related to its remoteness.
Andamooka Opal is typically of an exceptionally high quality, but has become more difficult to source in the last few years. Andamooka is reportedly very quiet at present with less than 50 serious miners.
White Opal
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White Opal is translucent with a creamy appearance that dominates the diffracted colours. While all the Australian Opal fields produce White Opal, the majority is mined in Coober Pedy.
Commenting that “there is in them a softer fire than the Ruby, there is the brilliant purple of the Amethyst, and the sea green of the Emerald - all shining together in incredible union,” Opal clearly impressed Pliny the Elder (23-79 AD), Roman historian and author of the “Historia Naturalis,” the world’s first encyclopaedia.
