cubic zirconia

Judith Ripka earrings set with Diamonique cubic zirconias
Photo courtesy of Scott Papper, GIA GG, AJP, CM (NAJA), Global Gemology & Appraisals
Species:  CZ (Synthetic Cubic Zirconia)
Mohs Hardness:  8 to 8.5 out of 10
Color:  Nearly every color, including colorless
RI:  OTL
Birefringence:  None
SR/DR/AGG:  SR
Pleochroism:  None
Spectrum:  Not diagnostic
Fluorescence:  Variable, not diagnostic
SG:  5.60 to 6.00

cubic zirconia facts

Multi-colored CZs set in a sterling silver designer tennis bracelet, by Caspian
Photo courtesy of Scott Papper, GIA GG, AJP, CM (NAJA), Global Gemology & Appraisals

Colorless CZs are commonly used as diamond imitations.

CZs are produced in nearly all colors to simulate sapphires, rubies, emeralds, garnets, topazes, peridots and more.

The natural form of cubic zirconia was discovered in 1892.  Synthetic CZs weren't invented until the 1930s.  They would later be mass-produced and introduced to the jewelry marked in the 1970s.

CZs weigh approximately 70% more than diamonds of the same size and proportions.
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Designer engagement ring, by Vanna K, featuring a cubic zirconia center with pavé-set CZ accents, in sterling silver
Photo courtesy of Scott Papper, GIA GG, AJP, CM (NAJA), Global Gemology & Appraisals