Cubic Zirconia was discovered in its natural state in 1937 by two German mineralogists, von Stackelberg and Chudoba. It was in a highly metallic zircon given to them by B.W. Anderson. The zircon contained tiny crystals that were determined to be the cubic form of zirconium oxide. 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.
To the untrained eye, cubic zirconia looks identical to a good quality diamond, but CZ has slightly less brilliance or sparkle than a diamond and more fire or flashes of color. The overall effect is so similar that it can even fool a trained gemologist on occasion. One great difference between cubic zirconia and diamond is weight; CZ is about 75% heavier than diamond. A piece of CZ the same size as a one carat diamond weighs about 1.75 carats. CZ is also more brittle than diamond and softer. Cubic Zirconia is also flawless, whereas diamond usually contains impurities and inclusions. Mohs scale hardness is also a major difference between the gleamers, with a Diamond setting the scale at 10.0 and CZ coming in at a minor 8.5; still tough but not to the scale of the Diamond.
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 commercially.
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 at right; 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 the desired level. The contents are kept molten for several hours to ensure uniformity.
To produce colors, oxides of cerium, copper, titanium, iron, nickel, and many other elements are added also.
