Zircon is a natural gem that gets confused with the cheap and common synthetic stone Cubic Zirconia (CZ). The two are totally distinct in their chemical & physical properties. Zircon's most popular color is blue and is considered an alternative birthstone for December. Top color Blue Zircon originating from Cambodia are highly prized. Some Blue Zircons have exceptionally bright and vivid coloration but, many are a pastel to light blue.