Gadolinium gallium garnet

Gadolinium gallium garnet (GGG, Gd₃Ga₅O₁₂) is a synthetic crystalline material of the garnet group, with good mechanical, thermal, and optical properties. It is typically colorless. It has a cubic lattice, a density of 7.08 g/cm³ and its Mohs hardness is variously noted as 6.5 and 7.5. Its crystals are produced with the Czochralski method. During production, various dopants can be added for colour modification. The material is also used in fabrication of various optical components and as a substrate material for magneto–optical films (magnetic bubble memory).^[2] It also finds use in jewelry as a diamond simulant. GGG can also be used as a seed substrate for the growth of other garnets such as yttrium iron garnet.^[3]

Gadolinium gallium garnet
General
Category	synthetic mineral
Formula	Gd3Ga5O12[1]
Crystal system	cubic
Identification
Color	transparent, colorless to light brown or yellow. May also be orange or blue.[1]
Mohs scale hardness	6.5[1] (other sources 7.5)
Luster	vitreous to subadamantine[1]
Specific gravity	7.05 (+.04, -.10)[1]
Density	7.08 g/cm3
Polish luster	vitreous to subadamantine[1]
Optical properties	Single refractive[1]
Refractive index	1.970 (+.060)[1]
Birefringence	none[1]
Pleochroism	none[1]
Dispersion	.045[1]
Ultraviolet fluorescence	moderate to strong pinkish orange in shortwave[1]

Another interesting aspect to this synthetic gemstone is that it exhibits both fluorescence under UV, and Phosphorescence (glow-in-the-dark) properties.

See also

• Micro-pulling-down
• Terbium gallium garnet
• Yttrium aluminium garnet
• GAGG:Ce (cerium-doped gadolinium aluminium gallium garnet)