CYCLOTRON IRRADIATION ON DIAMONDS

Modern diamond treatments can produce a vibrant array of diamond colors that capture the interest of many. One such treatment is diamond irradiation, which can produce blue and green diamond colors, depending on the color of the initially untreated diamond (in addition to yellow-brown if the irradiation is followed by annealing). Most diamonds today are irradiated with electron beams, but some older irradiation technologies made use of particle accelerators such as cyclotrons to produce the desired color. This type of irradiation would often leave distinct color concentrations in the diamond, called the “umbrella effect”, which was first characterized in the work of A.A. Schulke and H. Pough (The recognition of surface irradiated diamonds G&G Vol 7, No. 1, 1951, pp. 3-11). This effect, according to Schulke and Pough, is indicative of a diamond that has been irradiated through the culet using a cyclotron. Conversely, diamonds that have been irradiated through the crown will show “cubistic patterns of varying intensities of green” in the crown and will appear to have a dark ring of color between the table and culet when the diamond is observed oriented culet up. This study presents three such faceted diamonds, exhibiting color concentrations around the pavilion facets in two cases and around the crown facets in one case. The three diamonds were documented using UV-VIS spectroscopy, Fourier-Transform Infrared spectroscopy, and photoluminescence spectroscopy, photoluminescence hyperspectral mapping, followed by fluorescence imaging and cathodoluminescence imaging. Using these techniques we investigate the unusual color zoning patterns produced by cyclotron irradiation treatment.