Blue Zircon (or Blue Topaz) is the birthstone for December most commonly on the modern list, but Tanzanite also counts for the month. On the ancient list, Turquoise or was the selection for the month of December. Zircon is the stone of fun-loving, energetic December babies! You're always on the go, and always up for a challenge. Others see you as playful and generous, and you can always put a smile on someone's face.