Round Brilliant-Cut Cubic Zirconia.

Cubic zirconia is a man-made material used to imitate diamond and other gemstones. Commonly referred to as CZ. CZ has a thermal insulating property and diamond is a very efficient thermal conductor, therefore it is easy to separate diamond from CZ with a simple thermal conductivity test like that found in most diamond testers.

There is an extremely rare natural form of Cubic Zirconia but everything used in jewelry production is the man-made variety.

Gemological Information for Cubic Zirconia
Color	Colorless, Pink, Red, Yellow, Orange, Blue, Purple, Green and Brown
Crystal Structure	Cubic
Refractive Index	2.15
Durability	Excellent
Hardness	8.5
Similar Stones	Diamond, Zircon, Strotium Titanate, Sphene, Synthetic Rutile, GGG, YAG, Spessartite and Demantoid.
Treatments	None
Country of Origin	Man-Made
Cubic Zirconia Care
Ultrasonic cleaning	Safe
Steam Cleaning	Safe
Warm Soapy Water	Safe
Chemical Attact	No reaction
Light Sensitivity	None
Heat Sensitivity	Sensitive to High Temperatures