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New horizon for opal grading
[Thu 09/06/2011 11:57:32]
Opal Horizon, a Brisbane-based opal mining and wholesaling company, has launched a “globally quantifiable” grading system for Australia’s national gem.
According to Opal Horizon managing director Dave Horton, the lack of an easily understood and transparent system to identify and grade opal has restricted the growth of opal sales at the top end of the jewellery market.
“The result has been that Australia, which produces over 95 percent of all true gem quality opal available on the international market, has been unable to fully capitalise on the potential revenue this unique jewel should bring to the country.
“It has also meant that one of the most beautiful gems created by nature and one that should be an object of national pride, has been so reduced in status that it is seen by many, more as a tourist trinket than as the extremely rare and valuable gem it can be.”
Opal Horizon’s new grading system is based on the evaluation of three quantifiable grading criteria otherwise referred to as the 3 Cs – Category (defined by the presence and degree of host rock), Colour (opal face, body tone, play of colour, brightness, pattern, directionality and special attributes) and Cut (finish and polish, ease of setting, symmetry/balance and exclusion of defects).
Each of the 3 Cs is graded individually on a 100 points scale. The three scores are then added to reach a final quality score which is used to classify the opal into one of five categories:
Exceptional gem opal (285-300): Gemstone of exceptional quality, and very high visual impact. Very bright, full spectral play of colour.
Fine gem opal (240-284): Gemstone of high quality and high visual appeal. Bright to very bright, full spectral play of colour.
Gem opal (180-239): Gemstone of very good quality and good visual appeal. Bright, variable colour range
Commercial opal (90-179): Gemstone of moderate quality and appeal. Subdued to bright, variable colour range
Promotional opal (< 90): Low quality and appeal. Subdued, variable colour,
range and distribution.
Horton said the system will give jewellers a solid foundation for determining the market value of opals.
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