Zirconia are crystals created from gemstones that are visually and aesthetically comparable to diamonds. According to Swarovski, Zirconia has a comparable brilliance and hardness to diamonds, with a ranking of 8.5 on the Mohs Scale.
With the right selection and cut Zirconia can display the same or even better characteristics than a diamond, at a significantly lower price. In some respects Zirconia gemstones are more desirable to diamonds as they are flawless. From an ethical standpoint Zirconia are preferable because they are conflict free and produced in an environmentally responsible manner.