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. The birthstone of May, an emerald ring symbolizes the eternally returning spring. The velvety green color of emerald is a perfect match for spring and summer fashions.