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 cubic lattice, density 7.08 g/cm3 and Mohs hardness is variously noted as 6.5 and 7.5. Its crystals are made by Czochralski method and can be made with addition of various dopants for modification of color. It is used in fabrication of various optical components and as substrate material for magneto–optical films. It also finds use in jewelry as a diamond simulant.


Cause of Color :

Varies with dopants used.

Chemical Composition :

Gadolinium Gallium Oxide – Gd3Ga5O12

Classification / Type :

GGG is a man made material with a garnet internal structure. The term synthetic is not used to refer to this material, since it does not have a natural counterpart.

Crystal System / Forms :

Cubic System

Cuts & Uses :

Facetted cuts, beads, etc.

Dispersion : 0.045
Hardness : 5.5 - 6.5
Lustre : Adamantine to vitreous
Magnification :

Generally clean

Optic Character :

Isotropic (S.R.)

Pleochroism : None
Refractive Index / Birefringence :

1.970; Range: 1.920 – 2.030

Simulants (with separation tests) :

Y.A.G. (S.G.), Synthetic Cubic Zirconia (S.G., dispersion), Diamond (S.G., inclusions), Strontium Titanate (S.G., dispersion), Sphene (optic character, doubling, dispersion), Synthetic Rutile (optic character, dispersion, doubling), Demantoid (spectrum, inclusions, S.G.), Spessartite (spectrum, inclusions, S.G.), Malaya Garnet (spectrum, inclusions, S.G.)

Sources :

In a laboratory. No natural counterpart.

Specific Tests :

Moderate see through effect.

Spectrum :

Not characteristic

Synthesis :

Czochralski Method

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