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. One of the oldest gemstones in history, garnet is the birthstone of January. Garnet rings have been popular since Victorian times, and are treasured for their deep red color.