Q: Why Moissanite Rather Than Cubic Zirconia or Other Diamond Simulants? A: There are two types of cubic zirconia (c.z.) – machine-manufactured and hand-cut. Most people agree that machine-cut c.z. is hazy, and not brilliant. The hand-cut ones are a suitable diamond substitute, but still don't have the brilliance of true diamonds or moissanite. They also are less durable; c.z.'s register about a 9.0 on the Mohs hardness scale and moissanite about a 9.25, compared to 10 for a diamond (this is important for an engagement ring which will be worn daily). Other simulated diamonds, such as paste, glass, or quartz are not very popular since they are such poor substitutes. A company called Gemesis has started making man-made diamonds, but so far has only succeeded in making yellow fancy-colored ones, which are still 4 times more expensive than moissanite.