Thermochromic diamond analysis using in-situ absorption spectroscopy

Chameleon diamonds, a type of thermochromic gemstone, exhibit reversible color changes in response to temperature and light exposure, appearing greenish at room temperature and shifting to yellow when heated. This rare and visually striking behavior significantly affects both their aesthetic appeal and market value, making them of interest to gemological laboratories. Despite their importance, the underlying mechanisms behind these transitions remain poorly understood. To investigate the wavelength- and temperature-dependent behavior of thermochromic diamonds, an in situ absorption spectroscopy system incorporating a cryogenic stage and tunable light source has been used for this research. Our results show that greenish coloration can be induced by light with wavelengths below 680nm, with the most pronounced effect occurring near 420nm. Cooling the diamond from 550K to 300K produced comparable spectral changes, indicating a shared origin for the photochromic and thermochromic effects. These findings advance our understanding of color instability in diamonds and contribute to the development of more consistent and objective color evaluation protocols in gemology.