In the Middle Ages, opal was considered a stone that could provide great luck because it was believed to possess all the virtues of each gemstone whose color was represented in the color spectrum of the opal. Victorian superstitions were created by the established gem dealers to stop the rush to buy opals. They paid an author to attribute bad luck to the stone, though some believed this is avoided if opal is the owner's birthstone or if the stone was a gift. <br /> <br /> Opal is considered the birthstone for people born in October.