Brisbane (AUS) based Opal Horizon Ltd., employing some of the foremost opal authorities in the world, presented a new comprehensive gem quality opal grading system at the GIA Symposium in Carlsbad (USA).
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| Gem opal |
For both the trade and the consumer a clear understanding of a gemstone’s quality is a critical step in establishing its value. The Opal Horizon system proposes grading and evaluation standards that explain, define and measure the degrees of quality in precious opals. This new basis of evaluation provides a comparative frame of reference through easily understood classifications and grades using established nomenclature. This comprehensive and universal system for precious opal aims at promoting confidence and transparency.
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| Fine gem opal |
The new Opal Horizon grading system only applies to natural precious opal and is based on the evaluation of three quantifiable grading criteria.
The three quantifiable Cs
The three quantifiable criteria defined by Opal Horizon are Category, Colour and Cut.
“Category”: This describes the opal as one of three types each defined by the presence and degree of host rock in the opal.
“Colour”: The criteria applied to colour assigns points according to the opal face, body tone, play of colour, brightness, pattern, directionality and special attributes.
“Cut” : The quality of the cut is determined by the opal’s finish & polish, ease of setting, symmetry/balance and exclusion of defects.
Each of the 3 Cs is graded individually on a 100 points maximum scale. The three scores are then added and result in a final comprehensive quality score. This final score provides the accurate, comprehensive and credible grading of each opal and enables the opal to then be valued at current market prices for that grade.
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| Exceptional gem opal |
The 5 quality grades
The 3C quality assessment is used to classify the opal into one of the five following grades ranging from ’exceptional gem opal’ to ’promotional opal’.
| Quality classification | Total quality grade |
|---|---|
| Exceptional gem opal: Gemstone of exceptional quality, and very high visual impact. Very bright, full spectral play of colour. | 285 - 300 |
| Fine gem opal: Gemstone of high quality and high visual appeal. Bright to very bright, full spectral play of colour | 240 - 284 |
| Gem opal: Gemstone of very good quality and good visual appeal. Bright, variable colour range | 180 - 239 |
| Commercial opal: Gemstone of moderate quality and visual appeal. Subdued to bright, variable colour range | 90 - 179 |
| Promotional opal: Low quality and appeal. Subdued, variable colour range and distribution. | < 90 |
The launch of the new grading system by Opal Horizon marks the first step in a comprehensive global marketing and communications strategy for precious opal.
