Feature Gems & Gemology, Spring 2008, Vol. 44, No. 1

A History of Diamond Treatments

Although various forms of paints and coatings intended to alter the color of diamond have likely been in use for almost as long as diamonds have been valued as gems, the modern era of diamond treatment—featuring more permanent alterations to color through irradiation and high-pressure, high-temperature (HPHT) annealing, and improvements in apparent clarity with lead-based glass fillings—did not begin until the 20th century. Modern gemologists and diamantaires are faced with a broad spectrum of color and clarity treatments ranging from the simple to the highly sophisticated, and from the easily detected to the highly elusive. The history, characteristics, and identification of known diamond treatments are reviewed.