Here’s an interesting ring called Marie-Helene de Taillac Green Tourmaline Sugar Cube Ring.
Just like the name implies, a ‘sugar cube’ of green tourmailne is encased in rich, 22K gold and centered on a thin band. Believed to be a soothing stone, green tourmaline is also thought to inspire creativity and stimulate the imagination. The stone measures about 5mm square. The ring is a size 6.25.