Opal quality evaluation criteria How to evaluate Opal value Opal quality evaluation criteria affect the value of the factors are: base color, transparency, color change, style, brightness, color bar, color, defect, etc.
Base color: THE basic base color, black or dark OPal is the best, other things being equal, the price is higher than white.
Transparency: Opal’s transparency includes opacity – transparency.
Crystal opal refers to the transparency of opal, not to its crystal structure at the molecular or atomic scale.
The transparency of crystal opal generally ranges from translucent to transparent, while its color changes from intense to almost non-existent.
Sometimes the color of some “crystal opals” is so strong and dark that these opals are called “black crystal opals”.
Of course, this opal is very valuable.
Color change: color change is rich, color change throughout the whole gem, uniform and complete for the good.
Good quality Opal should show the red end of the spectrum, color change should have strong brightness and transparency, appearance change color bright.
Brightness: Brightness is the brightness and clarity of the color of the Opal table facing the observer.
The brightness of Opal is divided into bright, bright and dim, with bright as the best.
Opal ring how to evaluate the value of Opal style: The style of the color part of the Opal ring that forms the color varies.
The uniqueness and color of this part determine the grade of Opal style.
Special style has color pattern, the size and shape of the color area is almost the same, color bar: the thickness of the color bar in Opal is relative to the size and shape of the whole gem.
For example, a 3 mm round stone with a 1mm thick color bar is considered thick, and the stone can be carved into a bright convex shape.
The same color strip is considered to be of medium thickness on a 6 mm boulder, which can be carved into a convex cambered shape.
This color strip is thin on a 30 mm round stone, and the stone is flat.
Color: THE COLOR THAT DESCRIBES AN OPAL IS THE PREDOMINANT COLOR OR COLORS OF THE GEM WHEN THE TABLE IS UP.
Other things being equal, the longer the wavelength of an Opal color, the more valuable it is.
The most valuable black opal shows a distinct red color.
Blemishes: Blemishes are probably the most difficult to regulate in this system, as they can significantly affect the final score of an Opal.
There are many flaws that can affect the value of a well-crafted Opal.
A crack in the table can make an Opal worth a lot of money per carat almost worthless.
If IT IS RE-CUT AND GROUND TO A SMALLER size to ELIMINATE CRACKS, THE VALUE PER CARAT may be RESTORED, BUT THE total value of OPal will decrease as its quality decreases.
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