Structure : Isometric
Hardness : 8.5
Specific Gravity : 4.55
Refractive index : 1.833
YAG for a period was used in jewelry as a diamond and other gemstone simulant. Colored variants and their doping elements include; green (chromium), blue (cobalt), red (manganese), yellow (titanium), purple (neodymium), pink, and orange. As faceted gems they are valued (as synthetics) for their clarity, durability, high refractive index and dispersion. The critical angle of YAG is 33 degrees.
YAG cuts similar
to natural garnet, with polishing being performed with alumina or diamond (50,000
or 100,000) on common polishing laps. YAG has low heat sensitivity. As a synthetic
gemstone YAG has numerous varietal and trade names, as well as a number of misnomers.
Synonomous names include; alexite, amamite, circolite, dia-bud, diamite, diamogem,
diamonair, diamone, diamonique, diamonite, diamonte, di'yag, geminair, gemonair,
kimberly, Linde simulated diamond, nier-gem, regalair, replique, somerset, triamond,
YAIG, and yttrium garnet. It's misnomers include; synthetic diamond, and synthetic
demantoid, for green stones. Production for the gem trade lapsed after the introduction
of synthetic cubic zirconia, with little or no current production.