The tourmaline mineral group is chemically one of the most complicated groups of silicate minerals. Tourmaline has a wide variety of colours. Some crystals may consist of several colours, for example crystals might be green at one end and pink at the other, or green on the outside and pink inside, this type is called Watermelon Tourmaline. The most common variety of tourmaline is black schorl, first described by Mathesius in 1524. It may account for 95%or more of all tourmaline in nature.