Like waves on a clear blue sea, or twisting wind-swept clouds, these whimsical designs are an artistic expression of spirit and uniqueness. This birthstone of October has a luminosity and glow that makes an opal the treasure that it really is. The rainbow of colors on a neutral white background makes an opal ring a perfect match for any outfit. The birthstone of December, the tranquil azure color of a blue topaz ring can evoke thoughts of warm Caribbean seas on a cold winter day.