Cr:YAG, also known as Christmas Garnet, is a strikingly vibrant green garnet known for its hyperfluorescence and a highly sensitive red fluorescence. This unique combination results in captivating flashes of red and green, reminiscent of traditional Christmas colors, hence its nickname. With a Mohs hardness of 8.5, Christmas Garnet is exceptionally durable. It stands out as a true chameleon gem, responding to even the slightest amount of light from any wavelength by triggering its red fluorescence, which causes its appearance to change dramatically. This characteristic makes it an intriguing and dynamic choice for those seeking a gemstone with a lively and ever-changing play of colors.