This information, in conjunction with our article on distinguishing diamonds,  can help you separate diamonds from their imitators.

Identifying Synthetic Diamonds

Until relatively recently, gem-grade synthetic diamonds rarely appeared in jewelry. This is changing. Consult our article on identifying synthetic diamonds for advice on distinguishing natural or mined diamonds from their lab-created counterparts.

Properties of Natural Diamonds vs. Diamond Simulants

Properties Natural Diamond Type Ia Natural Diamond Type Ib Natural Diamond Type IIa Natural Diamond Type IIb Moissanite Cubic Zirconia
RI 2.417 2.417 2.417 2.417 2.648 – 2.691 2.15 – 2.18
Birefringence None None None None .043 None
Dispersion .044 .044 .044 .044 .009 – .104 .058 – .066
Optic Character Isotropic Isotropic Isotropic Isotropic Uniaxial + Isotropic
Pleochroism None None None None None None
Read Through None None None None None Slight
Luster Adamantine Adamantine Adamantine Adamantine Adamantine Subadamantine
SG 3.515 3.515 3.515 3.515 3.17 – 3.22 5.56 – 6.00
Hardness 10 10 10 10 9 ¼ 8 – 8 ½
Cleavage Perfect, four directions Perfect, four directions Perfect, four directions Perfect, four directions None None
Absorption Spectra Dark line at 415 and 478 nm, often more Increasing absorption towards blue end Variable, usually 504 Variable No sharp