DDG Ass #13 - Key Terms & Concepts PDF
Document Details
Uploaded by ComplementaryLutetium
Gemological Institute of America
Tags
Summary
This document explains key terms and concepts related to diamond fashioning. It discusses factors like craftsmanship, finish, and pavilion depth impacting overall quality and value. It highlights the importance of visual assessment over purely numerical parameters in evaluating diamonds.
Full Transcript
DDG Ass #13- Key Terms Craftsmanship—The care that goes into the fashioning of a polished diamond, as confirmed by its finish. Culet Size—The size of the facet at the bottom of the diamond where the pavilion mains meet. Design—A diamond’s physical shape, including its proportions and du...
DDG Ass #13- Key Terms Craftsmanship—The care that goes into the fashioning of a polished diamond, as confirmed by its finish. Culet Size—The size of the facet at the bottom of the diamond where the pavilion mains meet. Design—A diamond’s physical shape, including its proportions and durability, determined by decisions made during the fashioning process. Finish—The quality of the polish and precision of the cut of a fashioned gemstone. Girdle Thickness Percentage—Girdle thickness expressed as a percentage of average girdle diameter. Lower Half Length Percentage—The length of the lower half facets expressed as a percentage of the total distance between the girdle and the culet. Pavilion Angle—The angle formed by the pavilion mains and the girdle plane. Pavilion Depth Percentage—The distance from the girdle plane to the culet, expressed as a percentage of average girdle diameter. Key Concepts: A diamond’s pavilion makes a significant contribution to its brightness and fire. An estimate of a diamond’s pavilion depth percentage is usually accurate enough for grading and appraising. Generally, the greater the pavilion depth percentage, the steeper the pavilion angle. The purpose of a culet is to prevent abrasion and chipping on loose diamonds. Including design and craftsmanship in the cut grade gives a well-crafted diamond the recognition it deserves. Diamonds with thick girdles, steep crowns, or deep pavilions represent poor value because they appear smaller face-up than their weights suggest. Poor polish can make a diamond with even the best proportions look dull and hazy. Most diamonds have some symmetry variations, but the variations rarely affect appearance. Table percentage, crown angle, and pavilion angle play the biggest role in determining a round brilliant diamond’s brightness. It’s important to place more emphasis on the way a diamond actually looks than on its numerical parameters.
