Chemical composition -- Zirconium oxide plus yttrium or calcium.
Color -- Colorless when pure, but many different colors are provided by small chemical additives..
Optics -- R.I. 2.15-2.18 (singly refractive). Dispersion .058-.066.
Durability -- Hardness 8-8.5. Somewhat brittle, but wears well in jewelry.
Crystal structure -- Isometric (cubic) .
Specific Gravity -- 5.5-6.0.
Cubic zirconia (CZ) is the most widespread and inexpensive diamond simulant on the market today. While it occurs naturally in small quantities as the mineral baddeleyite, all of the CZ on the market is produced in the laboratory through skull-melting techniques. Vivid green CZ is sometimes referred to as C-OX, and CZ in numerous colors is frequently sold under various tradenames.
While it can often fool the unaided and untrained eye, CZ is easily distinguished from diamond by use of a thermal probe, by its greater specific gravity (when unset), and by microscopic examination of surface features and inclusions.