In order to best bring out the play of color 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.
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 millimeter-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.
Black Opal or Opal with a dark grey body shows the most brilliant play of colors imaginable. Crystal opal, which comes immediately after Black Opal in the hit list, should be more transparent with a deep play of colors. White or milky Opals show more diffuse colors and are the least expensive Opals.
The most important criterion for determining the price of an Opal, however, is the play of color, the colors as such and their pattern. If the color red appears when looking through the stone, all the other colors 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.
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