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.
In more detail
Every colorless stone sold as, or next to, a diamond is natural diamond, laboratory-grown diamond or a simulant. GIA names cubic zirconia as the most common diamond simulant today and moissanite as the next. A simulant gives itself away somewhere: in its optics, its weight or an instrument reading.
On a grading report
GIA doesn't grade simulants; it identifies them on an Identification Report.
Related terms
- 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.
- Cubic zirconia: Cubic zirconia (CZ) is a man-made diamond simulant. GIA names it as the most common simulant today.
- 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.
- Laboratory-grown diamond: A laboratory-grown diamond is a diamond that people grow with machines, by HPHT or CVD. It has essentially the same composition, crystal structure and properties as a natural diamond.
- Synthetic gemstone: A synthetic gemstone is made in a laboratory and has essentially the same chemistry and properties as the natural gem. A synthetic ruby is ruby, made by people.