Infrared microspectroscopy of natural Argyle pink diamond

The colour centre responsible for pink colouration in natural diamonds has not yet been identified. This paper presents optical and Infrared (IR) microspectroscopy in order to identify the degree of spatial correlation between the IR absorption peaks and the pink colouration of single-crystal natural Argyle diamond. The spatial distribution of the nitrogen B-centre (N–V–N3) is found to be anti-correlated with the pink colour. In contrast, no change is observed in any IR feature (including the B-centre) in response to driving the photochromism of natural pink diamond. We use these results to support a proposed mechanism for production of the pink colouration.

► Spatial correlation between IR absorption and pink colouration in Argyle diamond.
► Spatial distribution of “B-centre” seen to be anti-correlated with pink colour.
► Defects in pink graining possibly due to destruction of B-centres.
► No change seen in IR absorption bands (including B-centre) due to photochromism.
► Suggests “pink colour centre” shows no IR absorption.