GGG (gadolinium gallium garnet) is a man-made crystal used as an imitation of diamond. It is a close relative of YAG.
Properties
| Refractive index | 1.970 |
|---|---|
| Birefringence | None (singly refractive) |
| Optic character | Singly refractive |
| Dispersion | 0.045 |
| Specific gravity | 7.05 |
| Hardness (Mohs) | 6.5 (6 1/2) |
| Crystal system | Cubic |
| Pleochroism | None |
| Absorption spectrum | Not recorded |
Published values. They change a little from stone to stone. Our tools do not model GGG yet. Sources: GIA · International Gem Society · Gemdat
In more detail
GGG has about the same fire as diamond. It is much heavier than diamond, so a GGG looks smaller than a diamond of the same carat weight. It is soft, so it scratches fairly easily and often has rounded facet junctions.
Related terms
- Simulant: A simulant is a material that looks like a gem but has a different chemistry, structure and properties. Cubic zirconia, moissanite and glass are diamond simulants.
- YAG: YAG (yttrium aluminum garnet) is a man-made crystal used as an imitation of diamond. It is made in many colors, and the colorless crystal is cut as a diamond simulant.
- Cubic zirconia: Cubic zirconia (CZ) is a man-made diamond simulant. GIA names it as the most common simulant today.
- Diamond: Diamond is a single element, carbon, with every atom bonded to four neighbors in a cubic crystal. It is the hardest gem, Mohs 10.
- Specific gravity: Specific gravity compares a stone's weight with the weight of the same volume of water. It decides how much a stone of a given size weighs.
- Carat weight: Carat weight is the weight of a gemstone. One carat is 200 milligrams, a fifth of a gram, and it has 100 points.