As indicated by the derivation of its name, opal has centuries of history as a treasured gemstone. Historically, beliefs associated with the wearing of opal have varied. The early Greeks thought that opals gave their owners the powers of foresight and prophecy. Romans adored it as a token of hope and purity. Eastern people regarded it as sacred. Arabs believed it fell from heaven. In the nineteenth century, superstitions grew about the bad luck or fate that could befall one for wearing opal if it were not the wearer's birthstone. Today, these superstitions have diminished, but some people still believe it is bad luck to wear opals.

Opal has over one hundred variety and trade names, but the list of accepted or commonly used names is much shorter. The most important and most widely known opal is the precious opal. Precious opal may be subdivided further by color modifiers, white, black, pinks, and blue, which describe the body color of the opal. Australia is famous for its white and black precious opal. Fire opal, the bright red, reddish-yellow, orange body colored opal is the second most important opal commercially. Until recently, the best fire opal came from Mexico.