Professionally, black opal gemstones are classified based on their grading that exposes the world to different varieties of opal gemstones.
The purpose of grading is to rate the brilliance, pattern, and clarity of the black opal. Brilliance involves the vision of colors and patterns like pin, Chinese writing, ribbon, rolling flash, straw, and harlequin designs are common on black opals.
Black opals may also be categorized based on their various sources such as from Madagascar, Ethiopia, Honduras, etcetera. Amongst the best quality is the Australian black opal that originates from Lightning Ridge—the Black Opal Capital of the World.
Other types of natural black opals are chocolate opals and semi-black opals.
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