The name "opal" originates from the Greek word opallios, which means "to see a change in color." Opal is known for its' unique display of flashing rainbow colors called play-of-collor. This occurs in precious opal because it is made up of sub-microscopic soheres stacked in a grid-like pattern -- like layers of ping-pong balls in a box. As the lightwaves travel between the spheres, the waves diffract, or bend. As they bend, they break up into the colors of the rainbow, called spectral colors.
