Both of these signs have their own qualities of living life and personality traits where Capricorn zodiac sign is blessed with a Garnet birthstone while Aquarius is associated with an Amethyst birthstone. On that point, Garnet, a birthstone for January perfectly matches the uniqueness of Cap babies, and a vibrant purple stone Amethyst acts as a healing agent for Aquarians. To find common and different elements between these two zodiac signs, let's discuss how compatible they are in friendship and romantic relationships.