YAG (Yttrium Aluminium Garnet): an artificial material produced by the flux fusion method, chemically an Aluminate of Yttrium and Aluminum with the formula Y3Al2Al3O12. Transparent, ranging from colorless to various colors, it was used in jewelry from the mid-1960s through the 1980s as a Diamond simulant before being gradually replaced by other simulants considered more attractive, such as Cubic Zirconia and synthetic Moissanite. It crystallizes in the Cubic System, making it singly refractive, and has the same crystal structure as Garnets, despite lacking Silicon, which characterizes Garnet chemistry—hence its classification as a Garnetoid. It differs from Diamond by its weak dispersion, typically showing blue flashes on the pavilion.
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