Tourmaline group minerals have graced the cabinets of mineral collectors and museums for untold generations. Their colors and color patterns, along with their diverse shapes and associations, have assured their role as exqui- site showpieces. Their workability and durability have, in addition, made them favorites among connoisseurs of colored gemstones. Tourmalines, however, are much more than exquisite showpieces and beautiful gemstones. Their diverse crystal forms and unique structure, their variable chemical compositions, their intriguing physical properties, and their widespread...