THERE IS NO GOVERNING BODY WHICH SETS THE PRICES OF OPAL
Valueing Guide used by Miners and Dealers
TYPE
Black Opal which is regarded as the best then Boulder and White Opal(other characteristics being equal).
BRILLIANCE
The brighter the stone the better,valuable opals show brilliant flashes of colour while lesser quality opals have dull or subdued colours.The extent or overall completeness of the colour. The stone should face well, that is, there should be an even play of colour all over the stone with no dead patches of colour-less Opal.
PATTERN
Good,even and distinct patterns of colours;like rolling flash,harlequin,flag pattern and Chinese writting are very rare and highly prized.
BODY COLOUR
The degree of darkness in the body colour makes a stone more desirable by collectors. The blacker the body colour the more valuable the gem.
TRANSPARENCY
Light opal is more desirable the better the transparency and if lively brilliant colours are visible in crystal opals they are highly prized. Black opal is generally reduced in value if its transparent.
COLOUR
The dominant colour has value in this order: red,orange,yellow,green,blue,indigo and violet. However brilliance can override colour,a brilliant blue/green opal can be worth more than a dull red/orange opal. Nothing can compare to a "red on black" brilliant black opal from Lightning Ridge.
THICKNES OF COLOUR BAR
Black and Boulder opals with a thicker colour bar (cabachon) are generally worth more than a flat bar.
SHAPE
Oval,pear and other regular shaped stones will bring a higher price than irregular (free-form)stones.
SIZE
Smaller sizes under a carat are worth less per carat than larger stones.
IMPERFECTIONS
There are many different types of imperfections which will affect the value,although sand and other impurities that can't be seen from the top of the stone have very little impact on the price. Many collectors' stones have sand in the back of stones. Cracks or crazing will drastically reduce the value of a stone unless it can be recut.
TYPE
Black Opal which is regarded as the best then Boulder and White Opal(other characteristics being equal).
BRILLIANCE
The brighter the stone the better,valuable opals show brilliant flashes of colour while lesser quality opals have dull or subdued colours.The extent or overall completeness of the colour. The stone should face well, that is, there should be an even play of colour all over the stone with no dead patches of colour-less Opal.
PATTERN
Good,even and distinct patterns of colours;like rolling flash,harlequin,flag pattern and Chinese writting are very rare and highly prized.
BODY COLOUR
The degree of darkness in the body colour makes a stone more desirable by collectors. The blacker the body colour the more valuable the gem.
TRANSPARENCY
Light opal is more desirable the better the transparency and if lively brilliant colours are visible in crystal opals they are highly prized. Black opal is generally reduced in value if its transparent.
COLOUR
The dominant colour has value in this order: red,orange,yellow,green,blue,indigo and violet. However brilliance can override colour,a brilliant blue/green opal can be worth more than a dull red/orange opal. Nothing can compare to a "red on black" brilliant black opal from Lightning Ridge.
THICKNES OF COLOUR BAR
Black and Boulder opals with a thicker colour bar (cabachon) are generally worth more than a flat bar.
SHAPE
Oval,pear and other regular shaped stones will bring a higher price than irregular (free-form)stones.
SIZE
Smaller sizes under a carat are worth less per carat than larger stones.
IMPERFECTIONS
There are many different types of imperfections which will affect the value,although sand and other impurities that can't be seen from the top of the stone have very little impact on the price. Many collectors' stones have sand in the back of stones. Cracks or crazing will drastically reduce the value of a stone unless it can be recut.
