A single, unidentified producer, as we understand it, employs the HDSM method to cultivate YAG doped with cobalt (which we believe to be cobalt), exclusively for the gemstone market, with no known scientific applications. This material is available in a spectrum of Swiss blue hues, with the lightest being extremely faint. The outcome is an exceptionally brilliant and strikingly vivid blue gemstone. The deeper variants yield gems of remarkable quality, boasting superior dispersion, hardness, and refractive index compared to irradiated Swiss blue topaz, making them stand out in the realm of materials with a Mohs hardness exceeding 8. Among the most vibrant green to blue color ranges found in any substance are those of Yb:YAG, Co:YAG, and V:YAG.