Calibrated opal is the term for opal that has been cut and polished in oval sizes that are on a calibrated scale. For example, A 6 x 9 millimeter calibrated opal is a standard size opal, and would go in well in a set of earrings or a ring but if you wanted a pendant you would want a bigger calibrated stone like a 14 x 10 millimeter.
Most calibrated opals have been cut and polished in China were labor is cheap and fast. White opal is the most calibrated type of opal used because of its quantity available and it lower quality.
Calibrating machines have been made to automatically cut the calibrated opal so time and labor is cut down alot. Calibrating machines can be wasteful and cut away precious color. The machine cannot see the where the color bar is and may cut only the common potch. The human eye is still the best way to calibrate opal.
Calipers are used to measure the opal whilst being cut to size. The accuracy needed for calibration is 0.2mm.
Calibrated opal is a great way to start a jewelry range because it is easy to buy or get supply of the settings in quantity at a smaller cost.
The opal fields that supply the world with calibrated Opals are Coober Pedy, Andamooka, White cliffs and s Brazil. Coober Pedy is the largest source.
I have seen bags of calibrated opals in the thousands from China at very resonable prices. These gems have been distributed throughout the world by wholesalers and exporters alike.
For more information on opal cutting or purchasing opal. Please email email@example.com or you can call me on Skype My username is Blackopaldirect and it’s free!