A contribution to the understanding of pink color in diamond: The unique, historical «Grand Condé»

We recorded properties of a historical 9.01 ct pink diamond, the Grand Condé. It is a type IIa diamond that shows very weak absorptions at 860, 960, 1050, 1115 and 1156 cm− 1 that had not been reported yet. It shows an homogeneous fancy pink coloration with a subtle orangey component, and no discernable colored graining. However, we recorded an absorption band at 550 nm (2.2 eV), usually typical of pink diamonds with colored graining due to plastic deformation: this is the first time that these two properties are reported together for a single diamond. This shows that there is no direct connection between pink graining and the absorption at 2.2 eV.Second, we recorded a series of sharp absorptions at 573, 586, 594, 600 and 609 nm. We name it the 609 nm system. This system, probably related to the pink coloration, had only once been partially documented before, in three dark pink to red-brown diamonds. The 609 nm system is not related to the intensity of the pink coloration. Although this system might be vibronic in nature, it does not show the typical pattern for a simple vibronic structure.