By far the most successful simulant of diamond is cubic zirconia. It is also referred to as ‘CZ’ or sometimes just ‘cubic’. Cubic Zirconia gets its name from being the cubic crystalline form of zirconium dioxide (ZrO2) . It does occur in nature as the rare mineral ‘baddeleyite’ but it forms monoclinic crystals rather than cubic.
The original intention of producing cubic zirconia on any scale was for application in the optic and laser industries. The process was developed throughout the 1960’s and 70’s, mainly in France and the Soviet Union. As far as the jewellery industry is concerned commercial production began in 1976. By the early 1980’s the level of production was already huge. Initially the cost of cubic zirconia was high compared to today prices listed here.
Eventually, coloured varieties of Cubic Zirconia were developed so that today it is available in a wide selection of shades.
With a hardness of 8.25 on Mohs scale it is harder than most natural gemstones and it is also very dense, being approximately 1.8 times the weight of diamond. Importantly, its high dispersion is 0.058–0.066, which is higher than of diamond (0.044), meaning that it is optically very bright. So with the combination of hardness, brightness and low cost it is little wonder it is so widely used in jewellery.
In recent years there has been an increase of ‘coated’ cubic zirconia to gain a market edge. The application of a very thin film called a diamond-like carbon (DLC) is claimed to make the CZ slightly harder and appear more ‘diamond-like’. DLC coatings were developed for use on drill bits, engine parts, razors and the like.
Mohs’ Hardness: 8 - 8.5
Specific Gravity: 5.65 (Djevalite) & 5.95 (Phainite)
Refractive Index: 2.18 (Djevalite) & 2.17 (Phainite)
Optic Sign & Character: Isotropic
Durability: Very Good
Special Care: Normal Care
Possible Imitations: tends to imitate other gems