Tourmaline is distinguished by its three-sided prisms; no other common mineral has three sides. Tourmaline has a variety of colors. Bi-colored and multicolored crystals are common; crystals may be green at one end and pink at the other, or green on the outside and pink inside; this type is called watermelon tourmaline. Some forms of tourmaline are dichroic, that is they change color when viewed from different directions.
During the early 1900s, Maine and California were the world's largest producers of gem tourmalines. The Empress Dowager Cixi of China loved pink tourmaline and bought large quantities for gemstones and carvings from a mine located in San Diego County, California.
Almost every color of tourmaline can be found in Brazil. In 1989, miners discovered a unique and brightly colored variety of tourmaline in the state of Paraíba, and it has raised the bar on prices- over $5.000 a carat!