Opals are created when liquid silica gathers in the cracks of other types of stone and hardens. The pockets of silica reflect light in different colors depending on their shape and how the light hits them. The beauty of opals is in the play of different colors within the stone, and their individual fire.

There are several varieties of opal, including white, black, crystal, boulder, and fire, defined mainly by their base colors. White opals are the most well known opals, but the same beautiful play of colors can occur against a black, blue, or grey background. In contrast, fire and crystal opals are completely translucent.

Opal is the birthstone of October.