Green 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 Yellowish green to bluish green in appearance. Enhancements Green and Blue tourmaline is commonly heat treated to improve color. More information on gemstone enhancements. Heated to improve color. Heated to improve color.