Tanzanite engagement rings? Absolutely! Diamonds may be a girl's best friend, but Tanzanite engagement rings are a unique, original, and a far more affordable choice. Tanzanite is the new birthstone of December and has a unique purple-blue color. A tanzanite ring is one of the newest fashion trends and is a must for any jewelry collection. 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.