Tourmaline is the birthstone for October. Tourmaline is referred to as the ‘gemstone of the rainbow’ because it occurs in an incomparable variety of colours. Tourmaline is a dichroic gemstone, so depending on the angle from which you look the colour may be different or vary in intensity; although always more intense when viewed toward the main axis. Tourmaline often comes with two colours, known as bicoloured tourmaline. If the centre of a tourmaline is red and the area around it green it is given the nickname ‘watermelon’. There are colour change tourmalines, cat’s eye tourmaline and even neon coloured Paraiba tourmaline. Paraiba is often heavily included and often comes in intense blue and green, thanks to the element of copper which colours the stones.