Diamond treatments in the 14th Century were known to be an art form that significantly increased the value of the diamond. It was first in the early 14th Century when the true polishing and cutting to create new facet arrangements and shapes where thought to evolve (Balfour, 2000). As cutting technology advanced, it was natural that the diamond manufacturers learned how to improve the brilliance and color of a diamond. As a result is probable that a variety of coating techniques soon emerged. One of the oldest accounts of a master jeweler improving a diamonds appearance by treating the diamond’s surface with substances occurred in mid-century Italy. Benvenuto Cellini was commissioned to mount a diamond given by Holy Roman Emperor Charles V to Pope Paul III. Not only was diamond coating legal at this time, it was considered a widely accepted practice. To impress his colleagues, Cellini conducted the diamond coating publicly, to display his expertise. By applying a formula of pure gum mastic, linseed oil, almond oil, turpentine and lampblack to the base of the stone, he “seemed to remove from it any internal imperfections and make of it a stone of perfect quality (Cellini, 1568).” In doing so, the results were so dramatic that his audience declared an increase in the value of the diamond from 12,000 to 20,000 scudi (the precursor to the Italian lira)! Cellini’s writings further describe how the color of yellow diamonds could be improved by replacing the lampblack with and indigo dye. We know that the mastic and lampblack formula was employed for several centuries after Cellini, and a review of literature indicates it was the prominent treatment until the mid-20th century. Although formulas changed as the science of chemistry progressed, the application of blue coatings to diamonds were popular in the early 1900’s. Visit soon and enjoy Hadar Diamond’s next posting that will discuss contemporary diamond treatments…