The Diamond industry has developed a robust valuation model for Diamonds. Most gem valuers have been trained to carefully assess the "4 C's" or the Cut, Colour, Clarity and Carat weight. Unfortunately, these values are only 4 of the 14 categories that need to be assessed in order to finalize the value and (unfortunately) when you use a Diamond valuer to valuer an Opal the result is unreliable.
If you are looking to make a purchase or investigating a family heirloom, then these characteristics are a simplified method to give you some confidence. These would be the 3 most important factors if you are looking to make a purchase or get a basic idea of the value. Opal value is ultimately all about the colour, brightness and pattern.
Is best when multi-directional. You should be able to see different colours from variety of angles. Spin the gemstone around to see how many colours in the spectrum you can see. As a general rule if you can see pink or aqua you will generally be able to see all of the colours of the spectrum at some point. It is important to note that Opal colour can show completely different spectral colour bands in different 'types' of light. So, try looking at the Opal in daylight (sunlight), UV light, with a torch as you may see completely different colours revealed and this adds value!
Intense, brilliant colour is more valuable. High quality Opal will show you colour without direct light. We call this the 'miners test'. Simply take your Opal out of the bright showroom or sunlight and hold the Opal 'cupped' in your hand creating a shadow. Opals with `gem quality' colour will show intense flashes or display this colour even out of the direct light.
Patterns occur when the array of molecules are perfectly aligned in repeated sequences (blocks of molecules with the same structure). It is staggeringly rare and makes up only 0.01% of all Opals. Opals with ‘named’ patterns are far more valuable than regular Opals as they are so much rarer. This possibly accounts for the greatest confusion in the Opal industry as there may be two Opals side-by-side that look ‘basically the same’ (to a novice) yet one has a ‘named pattern’ which increases the value exponentially.
Patterns such as ‘pinfire', ‘chaff’, ‘straw’, ‘sheen’, ‘feather’ to name just a few and, when you find large blocks of colour you have the elusive ‘Harlequin’ pattern, the #1 most valuable commercially available gemstone in the world. To give you an idea of the rarity of this pattern we have cut and traded literally millions of Opals in over 60 years and have seen less than 10 genuine Harlequin patterned Opals. One Miners that we work with has been mining for 20 years and has never uncovered a harlequin patterned Opal. Watch
Be cautious of anyone who tries to tell you what your Opal is worth without first assessing the 13 characteristics of the Opal. Opal is in the TOP 10 most valuable gemstones in the world, so be sure to ask your valuer: "How many characteristics do you look at when valuing an Opal?" or ask which valuation program your valuer has used to assess value, or which certification they have done to qualify them to value and Opal.
Most importantly, once your valuer has determined the value ask: do you have any comparable examples for this value? Where could I see them? This question is important as valuers have been known to ‘google’ the value of an Opal by simply entering in the characteristics into a search and then using the result to define a value.
The problem with this is in the integrity of the search results (or lack of). It is a huge problem online that many thousands of tens of Opals that are advertised as "Australian" or "Natural" Opal are actually synthetic Opal, (a complex plastic) or Ethiopian Opal (which is regularly dyed, heated and treated) which is far less valuable than Australian Opal but looks exactly the same.
If it is just an "opinion" of value and does not answer the above characteristics it is basically not worth considering.
So please contact Australian Opal Cutters to find out the TRUE value of your Opal!