Semi Precious Round Tanzanite StoneHardness : 6.5 Appearance :Tanzanite, colored by Vanadium, is normally heat treated to bring out the intense purple, blue and greyish colors. The color seen depends on the angle they are viewed from. Under incandescent lighting, they can appear more violet. Can be confused with iolite. Tanzanite is also produced synthetically, and a new treatment of beryl produces a dark blue beryl that is very similar in color to tanzanite. Enhancements :Tanzanite is usually heat treated to produce violet-blue color. Violet-Blue Tanzanite is the result of heat-treatment.