Zircon is a naturally occurring mineral composed of zirconium silicate. It is found in a variety of colors including colorless, blue, yellow, brown, red, and green. Colorless zircon is especially valued for its high brilliance and fire, making it a popular substitute for diamonds. This gemstone forms in igneous, metamorphic, and sedimentary rocks and is one of the oldest known minerals, with some crystals dating back over 4 billion years. Zircon has a high refractive index and strong dispersion, giving it exceptional sparkle. It typically has a hardness of 6 to 7.5 on the Mohs scale, making it suitable for jewelry with proper care.