This mineral has been described as a stone with many facets. Naturally, it occurs as a colorless and transparent stone but can also be found in yellow, pink or pale grey. Topaz can also be made to be white, gray, pale green, blue, pink or reddish-yellow. About 20 years ago, the last known source of naturally yellow topaz became exhausted and therefore any remaining specimens can be quite valuable. Coating colorless topaz can create a rainbow effect known as Mystic Topaz. Coating can also be used to create sapphire blue and blue green topaz; these are not naturally occurring topaz colors. Yellow topaz is known as the modern birthstone for November.