Light source dependent colour perception in orange red garnets via spectroscopy and colorimetry

The coloration of garnets is governed by transition metal ions and crystal structure. This study established a rapid variety identification method for orange-red garnets based shifts in infrared absorption peaks. We quantified color parameters under standardized illuminants (D₆₅, A, and F₂) using the CIE 1976 L*a*b* space. The results revealed that the Mn/Fe ratio and Fe content critically modulate the hue angle (h°) of orange and red garnets. Illuminant A maximises chroma for red varieties, while F₂ light optimally displays orange-yellow garnets. D₆₅ provides a versatile source for routine identification and evaluation. This integration of crystal chemistry and colorimetry offers actionable strategies for optimising orange-red gemstone presentation.