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. November's birthstone, citrine sparkles like honey. Carry the warmth and glow of a golden sunset with you by wearing a beautiful citrine ring. 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.