The diamond market is the gem world’s last bastion of prissiness about gemstone treatment.
Whereas colored stone dealers have faced such facts of life as heating, irradiation and impregnation, and pearl dealers long ago made peace with culturing, diamond dealers still seem to be grappling with the realities of enhancement. A case in point: irradiated diamonds. Most specialists in fancy (natural) color diamonds won’t buy or sell stones known to have been irradiated—although these stones have been marketed for more than 50 years. As a result, irradiated diamonds are pretty much segregated from the mainstream and are sold exclusively by a tiny number of dealer-devotees.
The persistence of such separatism is ironic because diamonds were the first gem to be colorized in the lab with radiation. In 1904, British scientist Sir William Crookes set out to prove they could be tinted in this manner by burying small stones in radium bromide salts.
Although he succeeded, Crookes’ methods left something to be desired since diamonds turned a skin-deep green only, took months to do so and became radioactive in the process (something they remain to this day). But when, 38 years later, stones were greened more than superficially over days in a Michigan cyclotron without becoming radioactive for more than a few hours afterward, the stage was set to color diamonds in a safe, fast, permanent way. Now someone had to find out how to create a wider palette of colors. By coupling irradiation and heating, research gemologists began producing green, blue, yellow, brown and black diamonds on a commercial scale in the early 1950s.
The influx of varied-blue irradiated diamonds provoked as great a furor in the jewelry trade as the influx of cultured pearls had done some 30 years earlier. Then when the spreading contamination of natural pearl habitats in the 1950s and 1960s created increasing scarcities and drove up prices, trade acceptance of the cultured variety became a matter of economic necessity. With demand for fancy color diamonds the greatest in history, and their prices at all-time highs, economic necessity could finally give irradiated diamonds their greatest opportunity for broad acceptance.
Fooling the Eye
Although irradiation produces just about every diamond hue found in nature, it does so with varying degrees of success. Natural and treated golden brownish-yellow stones (possessing a color dealers call “burnt orange”) can’t be told apart merely by sight.
The same holds true for stones GIA would grade as “Fancy intense,” the lab’s highest color rating for fancy yellow diamonds. In 1992, some unscrupulous dealers took to submitting borderline “fancy-intense” stones to GIA which they gambled would eke out that grade. Those that did were zapped to deepen color and heighten value, then offered for sale as top-notch all-natural yellows. Luckily, labs caught their artificial coloring.