Origins Australia, Brazil, Ethiopia, Mexico, Peru, South Africa, Tanzania & Zimbabwe
Colors Found Various
Family Opal
Hardness 5.50 - 6.50
Refractive Index 1.37 - 1.52
Relative Density 1.98 - 2.50
One of the world's most coveted gemstones, Opal's name evolved from the Roman "opalus" which was derived from the Greek "opallios," meaning "to see a change of color." The Greek word was a modification of the ancient Indian Sanskrit name for Opal, "upala," which meant "precious stone." If one spoke in mixed tongues, then Opal would be opallios upala, "to see a change of color precious stone."
While their body color covers a broad spectrum, Opals are most prized for their unique fiery play of color, reflecting and refracting light into flashes of multiple colors.
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 colors that change with the angle of observation, called "play of color." 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 color.
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 color, 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 colors including cherry colored 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
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 color sets the spectral colors ablaze much like a storm cloud behind a rainbow (the black background provides contrast and intensity to this Opal's play of color). 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 jewelry 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 colors.
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 jewelry trends favoring color have seen an increase in Opal use among the world's leading jewelry houses.
Boulder Opal
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 (Gemological 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 colors, 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
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 color 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 favorably compared to Australian Opals, arguably the world's 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
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 color found in some Opals, its mint to apple green body color has made it very popular for jewelry. Trace amounts of nickel gives this Opal its unique color.
Jelly Opal
Jelly Opal (also known as Water Opal or Crystal Opal) is mined in Mexico and Australia. Offering an attractive blend of indistinct colors, it is transparent pure Opal with a gelatinous appearance and an occasionally pronounced opalescence (bluish sheen). The play of color is a subtle sheen dancing throughout the gem, rather than distinct color patches. When held out in direct light, Jelly Opal can display some of the most intense Opal colors. 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 jewelry 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 coloring. While it typically comes in blue or pink colors, greens are also occasionally found.
Semi Black Opal
With a brighter transparency than Black Opal, Semi Black Opal has a body color 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
White Opal is translucent with a creamy appearance that dominates the diffracted colors. 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 encyclopedia. With only 25% of mined Opal finding its way into jewelry, if you're looking to be impressed with Opals, there is no better place to start building your Opal collection than at GemsTV!
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