What is the name of the pattern in opal characterized by large, distinct, rectangular patches of play-of-color?

The pattern in opal that is characterized by large, distinct, rectangular patches of play-of-color is known as Harlequin. This term specifically describes the arrangement and appearance of the color flashes in the stone, which are arranged in a pattern resembling a checkerboard or a series of large, vivid "tiles." Harlequin opals exhibit an exceptional play-of-color that stands out distinctly against the background of the opal, making this pattern highly sought after by collectors and jewelers alike. The visual impact of this pattern is particularly striking and is often prized for its beauty and unique presentation.

Other patterns, while they may have their own distinct characteristics, do not encapsulate the specific layout of large rectangular patches as seen in Harlequin opals.