- The Federal Trade Commission considers it an unfair trade practice to use the word “perfect,” or any other word, expression or representation of similar import, as descriptive of any diamond that discloses flaws, cracks, carbon spots, clouds or other blemishes or imperfections of any kind, including inferior color and make, when examined by a trained eye under a corrected diamond eye loupe or other equal magnifier of not less than ten power. Because of flagrant misuse of this term in the sale of diamonds that do not fit this description, many jewelers avoid it use. The American Gem Society also prohibits its use by its members.
- Pink Diamond
- A term often used loosely in the trade to describe any diamond of pale reddish, purplish-red, purplish or violetish hue. Diamonds of colors other than pale reddish are sometimes described as rose pink, rose colored, peach blossom, heliotrope and similar terms. Such a diamond is called a “fancy.”
- The common name for a vertical, columnar mass of rock that cooled and solidified in the neck of a volcano. When these rock masses consist of kimberlite, they often contain diamonds. They occur in Africa, India, Russia, Arkansas and elsewhere.
- In weighing diamonds, one-hundredth part of a carat, each hundredth being called a point; e.g., 32 hundredths (.32) of a carat is said to be a 32-point diamond, or a thirty-two pointer. 100 points = 1 carat, 141+ carats = 1 ounce, and about 2268 carats = 1 pound.
- The relative smoothness of a surface, or the degree to which the finish of the surface approaches optical perfection. A well-polished diamond shows no wheel marks or burn marks under 10X.
- Polished Girdle
- A girdle that has been lapped to yield either a lustrous, curved surface or a series of flat, polished surfaces (facets).
- The reduction of a rough or irregular surface to a smooth flatness or curvature. In diamond fashioning, it is used to include both lapping, or blocking, and brillianteering, as well as the production of any facet; the final operation in fashioning a diamond, usually done with diamond powder on a horizontal disc, or lap, against which the diamond is held in a dop.
- Polishing Mark
- A groove or a scratch left by the lap on a facet of a diamond or other gemstone. Parallel grooves left on a diamond’s facet during its initial placement should be removed during the final polishing, so that they are not visible under 10X; otherwise, they are considered defect of finish.
- A term that meant originally the distribution of the mass of a fashioned diamond above and below the girdle. Use by diamond men has broadened its meaning to include the major factors that determine cutting quality; i.e., total depth as a percentage of the girdle diameter, table diameter, girdle thickness, facet angles, symmetry, and even details of finish.
- The Proportion Scope combines lenses and movable mirrors to project the silhouette of a diamond on a screen. Diagrams and scales on the screen, as well as a “zoom” range, enable the instrument to analyze the proportions of round brilliant-cut diamonds, as well as fancy-cut diamonds.