An engagement ring is more than a piece of jewelry. It is a promise, a hope, a life-altering event that lasts forever. Most engagement rings are set with a diamond or at least with a gemstone that came from deep within the earth - a product of Mother Nature. In contrast, a cubic zirconia engagement ring is set with a gemstone that came from a laboratory - a product of man. If you're one of those people who consider manmade gems to be amusing just because they are not "natural," consider the difference between a bitter, all-natural cacao bean and a bar of fine, manmade chocolate.
Cubic zirconia is a mineral called zirconium oxide. This is found in nature, but rarely. Synthesized, it is colorless unless another mineral is added to give it color. It is hard and, of course, has none of the flaws that a naturally occurring stone would pick up. The name is similar to the gem "zircon" but that stone is composed of zirconium silicate and is different. Cut like a diamond, only an expert can tell the difference between a cubic zirconia engagement ring and one set with a genuine diamond.
In scientific terms, a cubic zirconia engagement ring is quite similar to one set with a diamond. One of the ways a gemstone is judged is by dispersion rate. That's the degree to which a prism cut from the gemstone splits the light to show "fire." The dispersive power of a cubic zirconium is slightly greater than that of a diamond, so that a cubic zirconia engagement ring has more fire to it. The hardness rating is 8.3 compared to a diamond's rating of 10.
Color is one of the important C's that determine a diamond's value. While extremely few diamonds are really colorless, most cubic zirconia can be made to meet the perfect color rating. Because diamonds have a higher refractive rate, the cut of the two stones should be slightly different to optimize their brilliance. The biggest difference between the two gems is that a diamond is an efficient heat conductor while a cubic zirconia is a heat insulator.
Apart from its heat conductivity, a cubic zirconia engagement ring looks, cuts, and lasts like a genuine diamond. It is also less expensive per carat so that the same price will get a larger cubic zirconia engagement ring. The point of an engagement ring has nothing to do with the gem. However, the promise, the hope, the life-altering event are the same whether the ring has a gem or not.