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.

Source: en.wikipedia.org/wiki/Gadolinium_gallium_garnet

Gadolinium Gallium Garnet Properties

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.
Colors / Varieties: 
Colorless, red, blue, green.
Crystal System / Forms: 
Cubic System
Hardness: 
5.5 - 6.5
Specific Gravity: 
7.02 - 7.09
Cleavage / Fracture: 
Nil / Conchoidal fracture.
Optic Character: 
Isotropic (S.R.)
Lustre: 
Adamantine to vitreous
Refractive Index / Birefringence: 
1.970; Range: 1.920 - 2.030
Pleochroism: 
None
Dispersion: 
0.045
Magnification: 
Generally clean
U.V. Fluorescence: 
Spectrum: 
Not characteristic
Cause of Color: 
Varies with dopants used.
Specific Tests: 
Moderate see through effect.
Synthesis: 
Czochralski Method
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.
Cuts & Uses: 
Facetted cuts, beads, etc.