The birthstone of December, the intense deep blue color of a london blue topaz ring can evoke thoughts of warm Caribbean nights. Sapphire is the birthstone of September, and one of the most popular gemstones on the jewelry scene today. The deep blue color of a sapphire ring is just right for an evening out. 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.