Blue Topaz engagement rings? Absolutely! Diamonds may be a girl's best friend, but Blue Topaz engagement rings are a unique, original, and a far more affordable choice. 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. A long time favorite of jewelry designers, aquamarine is the birthstone of March. The diamond-like brilliance of an aquamarine ring is sure to attract attention.