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Cubic Zirconia


Cubic Zirconia is often abbreviated to CZ, is a synthetic stone used as a diamond replicate. It was first produced in 1977, and was originally marketed under the trade name of "Djevalite".


Cubic Zirconia (or CZ), is the cubic crystalline form of zirconium dioxide (ZrO2). The synthesized material is hard, optically flawless and usually colourless, but may be made in a variety of different colours. It should not be confused with zircon, which is a zirconium silicate (ZrSiO4).

Because of its low cost, durability, and close visual likeness to diamond, synthetic cubic Zirconia has remained the most gemologically and economically important competitor for diamonds since 1976. Its main competition as a synthetic gemstone is the more recently cultivated material, synthetic moissanite.

Gemmological Characteristics:

Cubic Zirconia is a cubic form of zirconium oxide that is created in a laboratory, thus it is not a mineral.  However, it was found naturally occurring once at one site in the 1930's, but has yet to be discovered since then.  The mineral with the same chemical composition as CZ, but in the monoclinic crystal system, is baddeleyite.

Cubic Zirconia has a hardness of 8.5 on Moh's Scale of Hardness and a white streak. It has a specific gravity between 5.65 and 5.95, and a density between 5.5 and 5.9. It is in the isometric crystal system with a 4/mbar32/m crystal class and an Fm3m space group. The refractive index of CZ is between 2.088 and 2.176, which is very high.  It has dispersion in the C-F area of the visible light spectrum of 0.060. Since CZ is transparent, it is often faceted. It can be made in nearly any colour and can be faceted into many cuts.


To produce CZ, baddeleyite (ZrO2) is heated to about 2300 degrees Celsius (almost 5,000 degrees Fahrenheit). This causes the mineral to become isometric. However, this change is not permanent, it reverses upon cooling; which is why a stabilizer must be added to prevent transformation upon cooling. If too much stabilizer is added, it results in a softer, less brilliant product. This requires such high heat that a special radio frequency "skull crucible" must be used to melt the Zirconia powder. This apparatus is shown in the picture and diagram above; it consists of a cup-like arrangement made up of a circle of copper fingers that is water cooled by internal plumbing. As the Zirconia melts, it leaves a thin shell that remains solid because it is cooled by the water in the copper fingers. As this occurs the Zirconia and the stabilizing oxide are added to fill the skull the desired level. The contents are kept molten for several hours to ensure uniformity. To produce colours, oxides of cerium, copper, titanium, iron, nickel, and many other elements are added also.


Cubic Zirconia was discovered in its natural state in 1937 by two German mineralogists, von Stackelberg and Chudoba. It was in a highly metamict zircon given to them by B.W. Anderson. The zircon contained tiny crystals that were determined to be the cubic form of zirconium oxide by x-ray diffraction. The two mineralogists thought so little of their discovery that they did not even give it a name; which is why it is still known by its scientific name, cubic Zirconia. It wasn't until the 1970's, however, that Soviet scientists learned how to grow the crystals in the laboratory. In 1977, it was first marketed under the trade name “Djevalite”. But CZ really took off in the 1980's when Swarovski & Co., a world-renowned Australian producer of leaded crystal, began producing cubic Zirconia for mass consumption.

Zodiac & Birthstone:

Gemini (20 May - 21 June)