Cubic zirconium was discovered in 1937 by two German mineralogists, M. V. Stackelberg and K. Chudoba. It became popular with jewelry designers in the 1970s after Soviet scientists under the direction of V. V. Osika learned how to “grow” the mineral in the Lebedev Physical Institute laboratory. Most of the cubic zirconium on the market is chemically composed of zirconium oxide and yttrium oxide. The two compounds are melted together at a very high temperature (almost 5,000°F [2,760°C]) using the skull melt method. This method uses a radio-frequency generator to heat the zirconium oxide. A careful cooling of the mixture produces the flawless crystals that become cubic zirconia gemstones.