Zircon comes closer to resembling Diamond than any other natural gem. Its strong luster and intense fire give it a real sparkle that is comparable to Diamond. However, its popularity is somewhat diminished by the fact that it is often perceived as an inexpensive Diamond imitation. Colorless Zircon is easily distinguished from Diamond by its strong double refraction and lower hardness. The brilliant luster and fire of Zircon, combined with its good hardness and range of colors, make it a most desirable gem. However, it does have some undesirable traits.