Zircon is a beautiful natural gemstone which has been used a diamond simulant for many years. Unfortunately, many people associate it with cubic zirconia which is a man made product. Natural zircons come in a variety of colors including, colorless, greens, browns, and most commonly a vibrant blue. The blue zircons are actually brownish or colorless zircons which have been heat treated. The heating of zircons is expected and accepted within the gem trade.