Cubic Zirconia Description

History

• Two German mineralogists, named M. von Stackelberg and K. Chudoba, discovered natural cubic zirconia in 1937. No one has found it in nature since. We call the stone by its scientific term because they did not think their discovery was very important, so they never gave the gem a name. In the 1970s, Soviet scientists learned to grow the crystal in laboratories to improve laser technology. In 1977, it was sold under the name Djevalite, but CZ popularity really began in the 1980s when Swarovski &Co., a renowned Australian crystal maker, began producing it in commercial quantities.

Production and Manufacturing

• To make CZ, scientists heat baddeleyite (zirconium dioxide, or ZrO2) to almost 5,000 degrees Fahrenheit using a process developed specifically for CZ production called a skull crucible. The skull crucible is a cup-like arrangement with an internal water-cooled system, that uses a radio frequency to heat the zirconium powder. The molecule becomes isometric, or cubic, but the change is not permanent. In order to make the change permanent, a stabilizer is like magnesium, calcium or yttrium oxide. The mixture kept molten for several hours until the uniform crystals form.

Properties

• Its scientific properties help differentiate CZ from other similar stones. It scores an 8.5 on the Mohs hardness scale that measures its ability to scratch other surfaces. A diamond scores 10.0. If you took a CZ piece the size of a one-carat diamond, the CZ would weigh about 1.75 carats. Generally, CZ is about 87.5 percent zirconium and 12.5 percent yttium oxide, the most common stabilizer. Some stones contain additional oxidizers to give them color.

Appearance

• Cubic zirconia is virtually flawless, a Grade F on the diamond clarity chart. Its fluorescence shows an unwanted hazing effect. Fluorescence cannot be seen by the naked eye, instead its measured using ultraviolet lights. Common CZ colors include pink, blue sapphire, orange, deep amethyst purple, green emerald, champagne and, of course, colorless like diamonds.

Cubic Zirconia vs. Diamond

• Cubic zirconia is commonly used as a less expensive alternative to diamonds. To the everyday observer, there are no obvious differences between a cubic zirconia and a diamond. Jewelers use special instruments to spot flashes of color or fire in the stone. Jewelers compare CZ to diamonds using the diamond guidelines for the four C's: cut, clarity, color and carat weight.