Cubic zirconia (CZ) is a man-made diamond simulant. GIA names it as the most common simulant today.
In more detail
CZ is much heavier than diamond, with a specific gravity of about 5.8. So in our simulator, a 1.00 ct T73 is only 5.48 mm across in CZ, against 6.48 mm in diamond. A CZ sold by weight looks small for its carat.
On a grading report
GIA doesn't grade CZ; it identifies it on an Identification Report.
Related terms
- Simulant: A simulant is a material that looks like a gem but has a different chemistry, structure and properties. Cubic zirconia, moissanite and glass are diamond simulants.
- Moissanite: Moissanite is silicon carbide, one silicon atom for every carbon atom, in a hexagonal crystal. It is a diamond simulant, and every moissanite in jewelry is laboratory-grown.
- Specific gravity: Specific gravity compares a stone's weight with the weight of the same volume of water. It decides how much a stone of a given size weighs.
- Identification Report: An Identification Report states what a material is, without color or clarity grades. GIA issues one for simulants and for diamonds with unstable treatments, such as coating or fracture filling.