During the 20th century, other synthetic materials were developed as cheaper substitutes for diamond. The most successful of these, first developed in 1976, is cubic zirconia – or CZ. As the name suggests, CZ has a cubic crystal structure and is singly refracting like diamond.
Importantly, it has a dispersion even greater than diamond and thus considerable fire. Together with its high refractive index, which is between that of zircon and diamond, CZ is also a very efficient diamond alternative.
However, although CZ is now a common diamond simulant it is still quite distinguishable from diamond. Because it is a synthetic substance, CZ is generally flawless, while most diamonds contain natural inclusions or other tiny flaws.
Further, CZ’s greater dispersion results in a ‘showy’ rainbow brilliance that makes it look different to diamond, particularly in larger stones. CZ has a hardness of around 8.5 to 9 on Moh’s scale that is acceptable for a gemstone; however, it scratches more easily than diamond. Everyday wear in an engagement ring, for example, will soon dull its sparkle.
Perhaps because of the similarity in names, cubic zirconia is sometimes confused with natural zircon, which is naturally occurring zirconium silicate, a quite different substance. However, because cubic zirconia is now usually referred to as CZ, this confusion is less common.
Undoubtedly, zircon will continue to be a useful substitute for diamond in the years to come.