Bi-color Tourmaline Gemstones Hardness 7.0. Tourmaline and opal are the birthstones of the month of October.
Tourmaline is the national gemstone of the United States.
Appearance Tourmaline of different colors often form within the same crystal. These are can be quite varied in appearance. Enhancements Occasionally heat treated to improve color. More information on gemstone enhancements. The other side is medium, strong, green, slightly included.