DIAMOND'S beauty lies in a property known as index of refraction which is the measure of a gem's ability to bend light within the stone and reflect it as a dazzling spectrum of color back through the top of the stone to the viewer's eyes. Diamond has an index of refraction of 2.41 which is significantly higher than the next closest natural gem, Zircon, which has an IR of 1.8 - 1.9. For comparison, Sapphire has an IR of only 1.76. While even a poorly cut diamond will present the effects of its extraordinary IR, it is essential that diamonds be properly cut to maximize their beauty. The figures below will help describe the effects of good versus poor cutting and how light reflection is affected.