Today the trade moves colored diamonds like nobody’s business. Every sale of naturally colored diamonds at auction seems to eclipse its previous high prices. Natural stones, referred to as fancy color diamonds, are the exclusive domain of the very deep-pocketed connoisseur. But consumers who’ve become enamored with these stunners can get their color fix too. Modern technology has produced some diamond stunners in all the colors of the rainbow at very affordable prices.
In the Beginning
How did this all start? To learn more about the genesis of colored diamonds we have to dig deep into the history of one very formidable scientist, Sir William Crookes (1832-1919). This Victorian era British scholar experimented with everything – almost. Strangely enough, Crookes had little formal education when he entered Royal College of Chemistry at age 16. During his career, he independently identified Thallium (No. 81 on the periodic table). Other research included experiments with vacuum tubes, known as Crookes tubes, which eventually led to the discovery of the x-ray.
While his total body of work made immense contributions in the scientific world, gemologists and jewelers may find his experiments with diamonds to be fascinating. After the discovery of radium (1898) it soon became apparent that diamonds exposed to radium rays in the dark respond by fluorescing and scintillate in an extraordinary way. Blue-white examples, Crookes noted, responded in the most dramatic fashion.
The Diamond Phase
In 1909 (by some accounts 1905), Crookes toured the Kimberley mines in South Africa as a guest of De Beers on his second African trip after one in 1896. This sparked his research in the luminescence of minerals – a study he continued until his death. After his watershed visits to South Africa, Sir William Crookes wrote Diamonds, 1909. The comprehensive tome covers all firsthand topics from collecting the gems, to the Diamond Office, and noteworthy diamonds in a wide range from bort to famous diamonds to meteoric stones. Even though it’s an early work, diamond fans will enjoy reading this foundational research volume.
Crookes used a couple of Kimberley diamonds for his experiments. One was subjected to radium, the other not. After a couple weeks, no appreciable change was noted. When the exposed diamond was placed in a tube of radium bromide with the salts touching all sides for six weeks – a dark bluish green color appeared. The color change was permanent, but only “skin-deep” in color, and rendered the stones radioactive. Not so terrific. Crookes donated that stone to London’s Natural History Museum in 1916 not long before he died.
Astonishing advances have been made in the field of radiation treated colored diamonds today, including the ability to induce the current wide array of colors. In our modern era, HPHT (high pressure high temperature) has become the widely used tool for commercial use in modifying a diamond’s color. In this process, treated stones may become colorless, blue, green, yellowish green to yellow, and even the wildly popular pink tints. “Outside of a well-equipped grading laboratory,” says GIA, “this form of diamond treatment is virtually undetectable.”