Tourmaline is a semi-precious stone that exists in a wide variety of colors: black, blue, brown, yellow, pink, green etc. Bi-colored Tourmaline crystals are common. Some crystals are pink at one end, and green at the other end: this type of Tourmaline crystal is called Watermelon Tourmaline.
Pictures of Tourmaline on stamps:Stamps featuring images of Tourmaline.
Tourmaline - Mozambique - 1979
Tourmaline - Switzerland - 1959
Tourmaline - Togo - 1999
Tourmaline - Brazil - 1989
Tourmaline - United States - 1974