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More than 90% of the world's quality gem opals come from Southern Australia, although it can be found in other parts of the world such as Brazil, Mexico, Czechoslovakia and USA (Nevada and Idaho).
In Australia opal is commonly cut to form Triplets, Doublets or Solids:
Triplets are a fine layer of opal which has been blackened on the back of the gem and is protected with a translucent acrylic covering. The fineness of the stone and the black backing make the stone appear darker and allow for a wide play of colours.
Doublets are treated in the same way as triplets but the opal is thicker. This tends to produce soft milky pastel colours.
Solids are much thicker and do not have a black backing. Solids from Coober Pedy and surrounding areas in South Australia tend to be more light blue and milky in appearance with specks of red and other colours throughout.
Superb black opal stones tend to come from the Lightning Ridge field, New South Wales, Australia. Deposits of white opal can be found in Japan and fire opal in Mexico and Honduras.
Boulder opals (where the opal material, because of the difficulties involved, has not been extracted from the host rock) tends to come from the Northern New South Wales fields and is commonly set in sterling silver.
Tiare Black Pearl has a range of Coober Pedy triplet, doublet and solid earrings and pendants set in 14ct gold as well as boulder opal sterling silver jewellery. |
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Background
Most opal is found where geothermal hot springs dried up during seasonal periods of rainfall and extended dry periods. Opal is a solidified jelly so it has no crystal structure and contains up to 13% water.
Precious opals are translucent to transparent and are distinguished by a combination of milky to pearly opalescence and an attractive play of many colors. These colors flash and change as a stone is viewed from different directions are caused by interference of light along minute cracks and other internal inhomogeneities.
Opal is extensively used as a gemstone. Precious opal has been a gemstone since Roman times. Opal was included among the noble gems and was ranked second only to emerald by the Romans. A beautiful opal called the orphanus was set in the crown of the Holy Roman Emperor. It was described "as though pure white snow flashed and sparked with the color of bright ruddy wine, and was overcome by this radiance." Opals are also set in the crown jewels of France.
The name opal is derived from the Latin word opalus, meaning seeing jewel. According to another theory the word opal comes from upala, a Sanskrit word simply meaning a stone.
The most striking quality of opal is its ability to refract and reflect specific wavelengths of light. The interplay of different wavelengths of light gives opal its unique visual appeal, and makes it one of the most sought-after gemstones in the world at all times.
Opals develop crazing if they are exposured to sun and allowed to dry out. In addition to cracking, loss of water causes loss of iridescence, therefore they need to be oiled regulary to keep the water inside. Opal also must be protected from detergents that dry the gem. And always remember, opals can be fairly brittle because they contain water.
Opal has been described in medieval times as a cure for diseases of the eye.
Modern Birthstone: October
Wedding anniversary: Opal is the anniversary gemstone for the 14th and 18th years of marriage.
Zodiac:
Opal along with tourmaline are birthstones of Libra (Balance): Sept. 23 - Oct. 23. |
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