Gadolinium gallium garnet

Jump to navigation Jump to search
Gadolinium gallium garnet, Gemological Institute of America


A colorless synthetic crystal of the garnet group that has been used as an imitation diamond. Gadolinium gallium garnet (GGG) stones were produced for a short time in the 1970s when the production of yttrium aluminum garnet (YAG) dropped. The GGG stone had a refractive index and dispersion nearly identical to diamonds. They were also hard enough to maintain clean faceted edges. However, their ingredients were much more expensive than YAGs and they had the unfortunate tendency to turn dark brown when exposed to sunlight. Additionally, their density was the highest of all imitation diamonds.

Synonyms and Related Terms

Raman spectrum of gadolinium gallium garnet; RRUFF

GGG; Diamonique II; Galliant

Physical and Chemical Properties

  • Luster = vitreous to subadamantine
  • Pleochroism = none
  • Fluorescence = moderate to strong pinkish orange in SW; inert to moderate orange in LW
  • Birefringence = none
Mohs Hardness 6.5 - 7.5
Density 7.08 g/ml
Refractive Index 1.970
Dispersion 0.045 (moderate fire)


Properties of Natural and Simulated Diamonds

Resources and Citations=

  • Gem Identification Lab Manual, Gemological Institute of America, 2016.
  • Wikipedia: [1] (Accessed Dec 2022)