GEMSTONE DURABILITY: DESIGN TO DISPLAY By Deborah Dupont Martin Knowledge of the durability of a gem- n today's market, most jewelers no longer deal solely stone is critical to understanding the I with traditional gems such as diamonds, rubies, sap- risks involved in the various setting, re- phires, and pearls. The increasing availability and popu- pair, and cleaning procedures commonly larity of a wide range of colored stones-tanzanite, used by the jeweler. Some gemstones need tsavorite, iolite, and tourmaline (figure l), to name a few - attention in display because of their reac- has opened a host of new possibilities in jewelry, but it has tion to heat and/or light. This article re- views gemstone durability considerations also added a n~ultitude'ofnew risks. for 31 species and their varieties as they While many in the trade are qualified to deal effec- affect design decisions as well as repair, tively with most of these stones, virtually everyone cleaning, and display of the piece. I11 all associated with the design, manufacture, and sale of cases, tlie'reader is advised to consult an jewelry should be aware of the potential problems of a experienced bench jeweler before attempt- particular gem material. The designer must lznow which ing any potentially damaging procedures. mounting will protect the stone best while still enhancing The recon~ii~endatioiisin this article are its natural beauty. The bench jeweler is responsible for offered from a gemological viewpoint and determining what stones are at risk in which setting or as g~~idelinesonly. repair procedures. The salesperson, who has the greatest customer contact, must not only be aware of these design and bench considerations, but must also lznow the rules involved in various cleaning procedures and be able to ABOUT THE AUTHOR advise the customer regarding precautions in care and Ms. Marlin is an instructor in the Colored Stones wear. Some stones even require special display considera- Department 01 the Resident Gemology Program at tions because they are sensitive to light or to the heat that the Gemological Institute 01 America, Santa Monica, California. Prior to joining GIA, she can be produced in a case. worked as a bench jeweler for 10 years. The most important factor in designing, setting, re- Acknowledgments. The following people were ex- pairing, or cleaning a piece of jewelry is durability. Essen- tremely helpful in reviewing the manuscript and tially, durability is the gemstone's ability to resist scratch- providing informat~on:Thornton Mann, Chuck At- ing (hardness),breaking (toughness),and effects caused by more, Dino DeGhionno, and Archie Curtis. Robert Kane was especially helpful in providing informa- heat, light, or chemicals (stability). The present article tion tor the chart and photographs. Thanks to examines gemstone durability and discusses the limita- Chris Keenan lor supplying photographs. Special tions and advantages of different settings, repair and thanks to Steven C. Martin lor providing many in- sights and useful information, as well as encour- cleaning procedures, and display practices for many differ- agement. The following graciously supplied jewel- ent stones. A chart is included to provide guidelines ry for photographs: The Altobelli Jewelers, The relating to durability and how it affects these procedures Gold Masters, Silverhorn, Steven C. Martin, and C. Y Sheng. Ruth Patcliick did a wonderful job for 31 gem species and their varieties. typing the manuscript. It is important to note that the following information V> 1987 Gemolog~calInstitute of America pertains to natural gems only, including common enhan- Durability of Gemstones GEMS & GEMOLOGY Summer 1987 63 cements, but not to any man-made materials. The most types of setting, cleaning, and repair pro- identity of a gem must be established before any cedures (e.g., diamond and corundum) may be used procedure beyond cleaning with warm soapy water in a wide variety of jewelry designs. For stones of may be attempted. If you cannot determine with lesser durability, however, possible weaknesses certainty whether or not a stone has been en- must be considered in the selection of a setting hanced, assume that it has and take the more style (see chart). A gem with poor toughness, such conservative approach. Many qualified bench jew- as topaz, would not be a candidate for a channel or elers will be able to perform procedures that are flush style setting; chances are the stone would not recommended here, but such an individual is break. Heat-sensitive stones such as emerald, not always available. This article, therefore, is tsavorite, and tanzanite could be subject to dam- intended to serve as guidelines (and guidelines age if set in a style that requires soldering near only) in these areas. Since there is some risk stones already in place. involved with any stone, consultation with a Some inclusions can increase the chance of qualified bench jeweler is always recommended. breakage during setting. Because such inclusions The information in this article was compiled vary from stone to stone, it is wise to examine the based on Webster (1983),Sinlzanlzas (1972))Palache stone under magnification before setting it. Frac- et al. (19441, Nassau (1984))and the GIA course tures or inclusions near the girdle edge, in particu- materials, as well as on the experience of the lar, contribute to the fragility of a stone, as does author and her communications with colleagues possible cleavage (e.g., topaz and kunzite]. In addi- in both gemology and jewelry n~anufacturing.A tion, a number of manufacturing jewelers have glossary is included to define some of the more reported to the author that some enhancements technical terms. (such as heating corundum, tanzanite, or blue zircon] may cause brittleness, which results in a DESIGNING AND MANUFACTURING gem that is more easily chipped and abraded. FOR GEMSTONE SAFETY Unusual and "problem" cuts create special AND WEARABILITY design problems. Many stones are asymmetrical or Durability determines the safest way a stone may are cut with very deep pavilions, and th~isrequire a be set and worn. Stones that are very resistant to special mounting. Other stones have extremely GLOSSARY Beads: Small portions of metal raised with a graver to hold burrs and other small rotating tools, from the background metal for the purpose of connected to a flexible shaft approximately 36 holding a stone in place or for decoration. inches (91 cm) in length that attaches to a motor. Bright-cut: An incised accent cut made with a flat A foot pedal controls the power. graver that both cuts and polishes metal at the Flux: A solution {usually a commercial preparation same time. containing borax) used to promote the flow of Burnisher: A highly polished oval-shaped steel solder and prevent oxidation in the area. blade that is used to smooth metal. Graver: A sharp tool used to cut and shape metal. Burr: A small cutting tool, available in various Several different sizes and shapes are commonly shapes and sizes, that is insetted into a flexshaft used for different types of settings. and used to excavate, shape, and cut metal during Reciprocating hammer: An automatic hammer the setting process. attachment used in conjunction with the flexshaft Chasing hammer: A lightweight, well-balanced in some setting techniques, hammer that is used in conjunction with a setting Setting punch: A small rod used with a chasing punch to work metal, e.g., to push a bezel onto the hammer to secure bezels. May be used for channel stone and, with various other hand tools, to create and flush setting also. raised and indented decorative patterns. Vector technique: A lateral back-and-forth Flexshaft; A machine that consists of a handpiece movement of opposite adjacent pairs of prongs, 64 Durability of Gemstones GEMS & GEMOLOGY Summer 1987 Figure 1. Tourmaline is one of the most popular of the "new" colored gems in the marketplace. This pendant (18.83 ct) and the two rings (5.54 and 13.50 ct) are all prong set. Jewelry courtesy of The Collector, La folio and Fallbrook, CA; photo 0 Harold &> Erica Van Pelt. thin girdles, or have sharp points that should be a ring, which is subject to much harder wear than protected; for these stones, a setting must be any other type of jewelry. If the customer insists designed that will protect the girdle or points that you put a fragile stone in a ring that will be without causing damage during manufacturing. worn with some frequency, try protecting it with Extra care must be taken with stones that are both creative forms of metalwork rising above the table, unusually cut and that do not withstand setting or select a setting style such as bezel that will procedures well. minimize the risk. How the item will be worn is another factor. There are two principal ways to design jewel- Many fragile gems, such as topaz, bicolored tour- ry: (1)design a piece and then find stones to fit the maline, tanzanite, lzunzite, and pearls, are best set design (commonly done when producing many in pendants, earrings, brooches, tie tacks, or in pieces from one design, and requires that the rings designed for occasional wear. Cuff links and stones used be readily available in calibrated sizes), bracelets are better suited for stones that are more and (2)custom create a piece of jewelry to display a resistant to abrasion and chipping, such as dia- specific stone (the method preferred for fragile or mond, corundum, jadeite, and chalcedony. Because unusually cut gemstones). Both types of design the table area of a gemstone is very difficult to require the use of one or more setting procedures, protect, it is best to choose a more durable stone for each of which -as described below - has its own Durability of Gemstones GEMS & GEMOLOGY Summer 1987 65 irns at low temperatures.