Zircon is renowned for its intense coloring, great luster, and high refractive index. A higher refractive index means the stone reflects light from more angles. In other words: more sparkle! With zircon’s sparkle comes impressive brilliance and “fire,” a gemological term for multi-colored flashes of light. You may recognize fire from another gem: diamond. In fact, zircon’s optical effects have led to centuries of confusion with diamonds.