What is an Opal Type?
Opal types are primarily based on the gem’s body color. This is the color that shows under a precious opal’s play of color, the flashing or moving colors across its surface. However, sometimes the form, matrix, or inclusions define the type. (Opals that show play of color are called “precious opals,” while those that don’t are called “common opals”).
The following three opal types are the most frequently used for jewelry and have opaque body colors that range from white to black. The Austalian Opal Dealer’s Association rates the body color from N1 (blackest) to N9 (whitest).
White (Light) Opal
The most widespread type is white opal (N7-N9). With a body color of white to light gray, it dominates commercial opal jewelry. This is certainly the most abundant precious opal type, with much of the Australian opal mines producing material with body colors in this range. For instance, Coober Pedy, the most prolific precious opal mine, primarily produces white opals.
Gray (Dark) Opal
Gray opals (N5-N6) have a medium gray body color, providing better contrast for the play of color on top. However, gray opals are less abundant than white opals. These gems…