Understanding opal patterns requires a close look at some of these pictures, so we recommend viewing this article on desktop.

What is an Opal Pattern?

Unlike mathematical patterns, opal patterns aren’t exactly repeating structures. Instead, gem dealers describe the shape, size, and directionality of opal’s play of color in terms of patterns. While the rarest and most valuable opal patterns really are geometric, most are simply descriptive.

In addition, few opals show only one pattern on their face, and even the best examples are less perfect than a first grader’s drawing. However, for appraising these gems, it’s important to recognize and name different opal patterns.

Because it’s easier to discern the play of color in black opal and boulder opal, most of the images and videos in this article have a dark or black body color. However, these patterns occur in all opal types.

Geometric Opal Patterns

Geometric opal patterns are some of the rarest and also most valuable. Of these, the most highly sought is the harlequin pattern, which shows a regular, mosaic-like play of color with more-or-less square patches of color.

This unusual boulder opal shows a few fantastic squares of color play, but I