On unusual deep-violet microcrystals of diamonds from placers of Ukraine

Ukrainian deep-violet diamond crystals have a distinctive broad absorption band centred at approximately 560 nm (17850 cm (super -1) or 2.21 eV). The intensity of this band is almost two orders of magnitude greater than that in a light rose diamond from Yakutia. Although previously this band was attributed to to the N-V centre because the absorption spectrum of the negative N-V centre in irradiated and unannealed type Ib diamonds is known to have an absorption band with a maximum at a similar wavelength, this assignment is not confirmed. At approximately 77 K, the 17850 cm (super -1) band displays no fine structure that unambiguously shows that it cannot be the band at approximately 2.2 eV, commonly attributed to the N-V centre. This band is probably caused by 'plastic deformation', typical of pink diamonds from the Argyle field.