Topaz is an aluminium silicate that contains hydroxyl and fluorine and pure topaz is colorless. The impurities of topaz cause variations in color. The use of topaz goes back to Egyptian times when the ancient Egyptians thought that yellow topaz was yellow because of Ra the Sun God. Some believe that "topaz" was attained from the Old French word "Topace" and Latin "Topazus", the root of which is in the Greek word "Topazios" or "Topazion"; the ancient name of an island in The Red Sea. In there, the ancient Greeks mined a yellow gem that they thought was topaz. It is thought that the gem mined by the ancient Greeks was actually "chrysolite". The name of topaz may also have been brought about by an ancient Indiana language, which means fire.