Surface flaws consist of nicks or cavities in the face of the stone either above or below the girdle. The brilliancy of the diamond hides these flaws when the diamond is clean, but when clouded with soap and dust these cavities fill up and show plainly.
Diamonds are so brilliant, the radiance from the facets so bewildering to the eye, that the flaws cannot be seen by the human eye unless the imperfection is pronounced and at the top surface of the diamond. Each facet of a diamond (by reason of the method of cutting) is a window looking down a clearly defined walled chamber, like a hall-way to the culet. With a one-inch loup or magnifying glass such as watchmakers and diamond dealers use, it is possible to clearly look down through each facet and its hall-way to the culet, and observe throughout each chamber the very slightest imperfection if one exists, thus thoroughly examining and exploring the entire diamond.
Diamond brilliancy is of two kinds: “surface brilliancy” and “internal brilliancy.” Light falling vertically on a diamond is reflected back in straight, unbroken rays. This constitutes “surface brilliancy,” Light falling in a slanting direction is partly reflected and partly enters the stone; that part which enters is refracted or bent and causes the “internal brilliancy.”
In a perfectly cut diamond, the facets are so carefully arranged that entering rays of light jump from wall to wall of this transparent enclosure and emerge again at the very point of entry. Cleverly arranged mirrors sending a ray of light from one to all the others and back again to the first will produce the same effect. Lights entering a diamond are reflected, refracted and dispersed. The dispersion of a ray of white light separates it into its component color rays. These are the spectrum colors often seen radiating from a diamond. Placing a diamond in the sun’s rays and holding a sheet of white paper at the proper angle to catch the reflections from the stone clearly shows these colors.
Modern American Cut Diamonds
Brilliancy is often said to be the most important quality of a diamond, but that is not true. Yellow diamonds are more flashingly brilliant than white stones that cost much more. In each color grade, greater brilliance determines higher value over stones of the same color grade with less brilliancy. The diamond is the hardest known substance in the world, cutting and grinding all other known hard things, but itself only cut and ground by its mates.
Because of their hardness, diamonds worn by many previous generations remain as brilliant as they were in the beginning and they will continue so to the end of time.