Natural zircon (not to be confused with cubic zirconia) has been used to create convincing diamond imitations. However, this gem is doubly refractive and has a high birefringence. Diamonds have no birefringence. 2.35-ct radiant step emerald-cut zircon. © Dan Stairs Custom Gemstones. Used with permission.
Article: What is Gemstone Birefringence?
Credit: Dan Stairs Custom Gemstones
|Natural or man made||Natural|