Opals have been prized by Western cultures since ancient Roman times. In fact, anthropologists have found ancient opal artifacts dating back almost 6,000 years, and the Aztecs were mining opal nearly 500 years ago. Traditionally, opal has been known as the most magical of stones because it displays all colors combined. Middle Eastern folklore declares that opals are created by lightning, and in Europe, opal symbolizes purity and hope.
Opal is known for its phenomena, play-of-color. This occurs because opals are made up of sub-microscopic spheres stacked in a grid-like pattern similar to layers of ping-pong balls in a box. This structure breaks up light into spectral colors. The colors you see depend upon the sizes of the spheres.