The name "topaz" is derived from the Greek topazos, "to seek," which was the name of an island in the Red Sea that was difficult to find and from which a yellow stone (now believed to be a yellowish olivine ) was mined in ancient times. In the Middle Ages the name topaz was used to refer to any yellow gemstone.
Pure topaz is transparent but is usually tinted by impurities; typical topaz is wine or straw-yellow . They may also be white , gray , green , blue , or reddish -yellow and transparent or translucent. When heated, yellow topaz often becomes reddish-pink . It can also be irradiated, turning the stone a light and distinctive shade of blue.