Sometimes the best designs are the simplest designs. These rings focus on the beauty and brilliance of the gemstones and the sheen of the 14K gold that encompasses them. 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. 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.