GGG | Gemopedia

Gadolinium gallium garnet, thankfully abbreviated to GGG, is a man-made diamond simulant that entered the market in the 1960's. Today it is rarely used as a gemstone, and is instead manufactured for optical and industrial uses. The Czochralski method of gem synthesis involves the melting of various elements in a platinum crucible. A small gem crystal (called a seed) and attached to a rod is then dipped into the melt and slowly pulled away as the crystal grows around the seed. For this reason, the Czochralski method is also known as crystal pulling. Synthetic gems have the same chemical, optical, and physical properties of their natural counterparts, but are a more cost-effective alternative to a natural gem.
Alternate
Names
Gadolinium Gallium Garnet. 3 G, Triple G, Galliant
Colors
Colorless, Light Brown, Yellow, Orange, Blue, Green, Lilac, Red, Pink

GGG Classification

Common Name

GGG

Species

GGG

Variety

Colors

Colorless, Light Brown, Yellow, Orange, Blue, Green, Lilac, Red, Pink

Alternate Names

Gadolinium Gallium Garnet. 3 G, Triple G, Galliant

Gemstone Groups

Key Separations

Negative reaction to diamond tester, OTL RI, lack of doubling, fluorescence, SG and pavilion flash.

Comments

Misnomer: synthetic diamond. GGG has a moderate see-through effect. Stones will have an orange and blue pavilion flash effect. A 6mm round stone will weigh about twice as much as same size diamond.

GGG Optical Properties

Transparency

Transparent

Refractive Index

Over the Limit 1.97-2.03

Birefringence

Optic Character

NA

Optic Sign

NA

Polariscope Reaction

Singly Refractive (SR)

Fluorescence

SWUV: moderate to strong pinkish orange
LWUV: inert to moderate orange

CCF Reaction

Pleochroism

None

Dispersion

Strength: moderate fire Value: 0.045

Comments

GGG Chemistry & Crystallography

Chemical Name

Chemical Formula

Gd3Ga5O12

Synthesis

Czochralski pulled

Crystal System

Cubic

Classification

Nature

Synthetic

Crystallinity

Crystalline

Comments

GGG Characteristic Physical Properties

Hardness

6.5

Streak

Specific Gravity

6.95-7.09 Typical:7.05

Toughness

Varies

Inclusions

Generally inclusion free but might have gas bubbles.

Luster

SubAdamantine

Stability

Fracture

Conchoidal

Cleavage

None

Comments

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