|There is no naturally pure cubic zirconia mineral, it was created as a diamond simulant. The transparent variety has similar coloring and sparkle to a natural diamond. (See second gemstone below.) With a hardness around 8 and better color dispersion than quartz it is a far more effective simulant.
Over time various colorants were added to the process to create a rainbow of CZ (cubic zironia) colors. The CZ is created by recrystallizing from a zirconium oxide melt in a process called "skull melting".
To see the process you can go to the page where it is explained in more detail and via animation. CZ skull-melting animation
The champagne colored stone was cut by the author. The other stones are all commercial cuts. CZ jewelry has become such a commodity business that the stones are now cut in mass automatically and cost only a few cents per carat for most commercial cuts.
The darker colored CZ commands slightly higher prices than the clear material. This is likely due to more limited production.