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Type of opal

Opal classification

Opal is found in many varieties, but precious opal represents a remarkably small percentage of the total opal mined. Fine gem quality opal is rarer than diamond that possess “IF” clarity D color. It is a more natural gem, and is a thing of beauty and obvious worth, even in its natural state.

For centuries, opal lovers have used opal’s diversity to classify and re-classify opal. One book lists almost 400 opal types. Fortunately, the jewelry industry groups opal into a few broad—and more manageable—categories. Each category has its own unique qualities and value factors. The opal categories commonly used in the trade are:


  • Black opal—Background color ranges from black to dark gray, but should appear black in reflected light; shows play-of-color


  • White opal—Background color ranges from translucent white to medium gray; shows play-of-color


  • Crystal opal—Background ranges from transparent to semitransparent; shows exceptional play-of-color
  • Water opal—Background ranges from transparent to translucent; shows faint play-of-color


  • Boulder opal—Includes host-rock fragments, or matrix, as part of the finished gem; shows play-of-color


  • Fire opal—Background color ranges from transparent to translucent reds and oranges to yellows; may or may not show play-of-color


  • Assembled opal—Precious opal layers, or layers of precious opal and other material, cemented together to improve durability and appearance