Birthstones by Month December: Honoring Traditions and Future Goals Hello, December babies! Turquoise is one of the most fascinating birthstones by month December and is also well-known as a Sagittarius birthstone because of its serene hue, which aids Sagittarians in bringing serenity and peace to their adventurous personalities. Turquoise can also represent the union of heaven and earth for Sagittarius angels because of their qualities of honesty, adaptability, and optimistic influence.