Tourmaline and diamond ring, early 20^th century. Tourmaline is famous for both its range of colours, and also its pleochroism – meaning its ability to split light into two or more different colours depending on the orientation of the crystal. This central tourmaline is beautifully cut to take advantage of this – its facets internally reflect and mix a range of different colours between lush green and marine blue. This beautiful and evocative stone is set within a delicately pierced and millegrain mount set with two early 20^th century circular-cut diamonds.