![]() Often adding confusion, there can be several rows of facets in this region and all of them can be referred to as mains. When there is more than one row of either triangular or kite-shaped facets between the lower girdle facets and the culet (or culet facets), the facets of the intermediate rows are called mains or pavilion mains. 2-03), the kite-shaped culet facets may also be referred to as kite facets. Crown mains usually touch the edge of the table and the edge of the girdle.Ĭolored stone cutters refer to pavilion facets that touch the culet area as culet facets, even though the facets are not parallel to the table (this type of labeling is common in diagrams generated by software used by colored gem faceters called GemCad). Crown mains ( bezels in the diamond trade) are usually kite shaped, and refer to a position between the stars (triangular facets bordering the table) and the break or upper girdle facets (bordering the girdle). The table is often the largest central facet on the crown. Although there may be inconsistencies in how the trade describes certain facets, these are the most commonly used terms. Re-cutting these to improve cut quality will usually sacrifice the color, substantially decreasing its value.įig. These gems were cut intentionally with the culet skewed to one side. The culet can be considerably off center in native-cut gems (see Fig. The crown can be somewhat more orderly, but can be as irregular as the pavilion. The facets are often very irregular on the pavilion. If a pavilion depth is too shallow, you will see through the gem, called windowing, and if it is too deep, the gem will appear dark overall.Ī lot of what is referred to as “native cut” (discussed in detail below) can be exemplified by Figures 2-01 and 2-02. ![]() Pavilion depth (expressed as a percentage of the diameter) can also vary. A gemstone's crown height (listed as a percentage of the diameter) can vary from deep to shallow, depending on the cutting style. The total depth of the gem is the total thickness of the gem from the table to the culet. Sometimes there is a small facet at the culet that is parallel to the table. If the pavilion facets come to a point at the bottom, that point is called a culet. The pavilion is the bottom portion of the gem. The girdle is the outer edge of the gem, where metal grips the stone to hold it in place in jewelry or art. Usually gems are fashioned so that the observer is looking through the table, the flat top facet on the crown (top portion) of the gem, to see how light has been collected and returned back to them to view. This illustration shows the common features of a gem and irregular pavilion facets. 2-01) that the facets themselves defy normal naming conventions.įig. However, many gems cut in certain parts of the world have such irregular pavilion facets (see Fig. Generally speaking, most faceted gems have common features, like a crown, girdle, and pavilion. 2-14) were made using the program DiamCalc adjustments were made to the refractive index to represent the gem material being demonstrated. We now need to define aspects of cutting styles to establish some common language, with a focus on basic faceting styles, and a short discussion on cabochons and beads.Ī note on the wireframes or depictions of facet arrangements used throughout: These were created from scans of real gems to illustrate aspects of gem cutting. In Part 1 of this series we reviewed the seven major factors that affect the price of a colored gemstone: color, uniformity of color, country of origin, size, clarity, shape, and quality of cutting. ![]() This web version of the original series is divided into five separate articles and reflects minor stylistic edits to the original. GIA researcher and cut expert, Al Gilbertson, examines the elements of cutting, investigates the choices and tradeoffs a cutter makes and why, and provides guidelines for assessing various aspects of cut quality for colored gemstones. Originally published in GemGuide in 2016, this comprehensive series examines the quality factors that influence the value of colored gemstones, with a specific emphasis on the role cut quality plays in determining the value of faceted gems. Photo: Orasa Weldon/GIA Part 2 of 5 in the series: Value Factors, Design, and Cut Quality of Colored Gemstones (Non-Diamond) ![]() Applied Jewelry Professional ™ Online DiplomaĪmetrine cut by Christopher Wolfsberg.
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