Natural Watermelon Tourmaline Faceted Pear Drops Briolette Length 4 inches and Size from 6mm to 8mm approx. Tourmaline (tur-mah-Leen) is a crystal boron silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is classified as a semi-precious stone and the gemstone comes in a wide variety of colors.