Value Factors, Design, and Cut Quality of Colored Gemstones (Non-Diamond)

Posted on April 1, 2020 by Al Gilbertson, GG (GIA), CG (AGS)

In this comprehensive article, the author discusses the value factors of colored gems in five parts. Parts one and two appeared in Gem Market News, January/ February 2016, Volume 35, Issue 1. Parts three and four appeared in Gem Market News, March/April 2016, Volume 35, Issue 2. What follows is the fifth and final part.

Fig 5 010a
Part 5: Craftsmanship and Summary
Part 1 discussed the major value factors that affect the price of a colored gemstone which included cut quality. Part 2 defined aspects of cutting styles to establish some common language, with a focus on basic faceting styles, and a short discussion on cabochons and beads. Part 3 spoke about dark patterns in a gem and what causes them. Part 4 explored many of the factors used in the trade (rightly or wrongly) to assess relative value as well as explained some of the additional choices cutters make and why. Part 5 will discuss craftsmanship’s bearing on cut quality.

Wireframes or depictions of facet arrangements (such as Fig. 5-07) are from scans of real gems so as to illustrate certain aspects of gem cutting. Face-up patterns (such as Fig. 5-03, right) were made using the program DiamCalc; adjustments were made to the refractive index to represent the gem material being demonstrated. DiamCalc cannot show double refraction.

Craftsmanship is a broad term that denotes how much attention to detail the cutter gave to the finished gem. Most colored gemstones are cut in a variety of fancy shapes with many facet variations. Because of that, some aspects are less critical than others. Minor deviations of craftsmanship aren’t as critical as achieving the optimal color. However, very careful attention to detail is rewarded by being able to demand a higher price. As the general value of the type of gem goes up, this becomes…

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