FANCY LIGHT BLUE DIAMONDS – A NEW TREATMENT

Natural Blue and Violet diamonds are extremely rare in nature and thus very desirable and valuable in the Gem trade. Only one source of these hydrogen rich diamonds is know the now closed Argyle mine in Australia (Bogert et al., 2009). Green and Yellow diamonds are typically associated with irradiation treatments that can create desirable and hence valuable diamonds in the gem trade. However recently the GIA (Gemological Institute of America) has identified a few light blue to purple diamonds as “Treated color” (artificial irradiation). This is unusual as the starting material needed to create these colors is pink/brown and may be quite valuable (Johnson et al., 2020). Study of these diamonds revealed features typical of natural Pink type Ia (nitrogen bearing) diamonds whilst Advanced Spectroscopic techniques confirmed that they are type Ia diamonds consistent with Pink Argyle type diamonds. However, the blue color contradicts these properties. A very unusual combination of spectral features create this blue to purple color and it is a great example of color engineering in diamond. With further irradiation experiments at GIA, we will recreate this treatment aiding in the identification of this diamond color.