World Of Gems Conference 2017 Proceedings Book

WORLD OF GEMS CONFERENCE V - 17 - SEPTEMBER 2017 T oday, despite modern technology, the global mining of gemstones and easy access through broad marketing channels, gem quality rough remains exceptionally rare and the worldwide demand far exceeds supply. The industry is dependent on gem treatments to increase supply to try to satisfy the demand. Likewise, the nature of a gem’s quality is often essential to proper valuation. Accurately identifying the nature of a gem requires the gemologist to distinguish not only between treated and natural, but also between the various treatments encountered in today’s market. It is generally less challenging for the gemologist to deter- mine that a particular gem has been treated, than to conclude that it is natural (has not been treated). Information about new treatments are almost always achieved after the gem treatment technique is recognized in the laboratories. There are very few examples of a gem treatment being disclosed prior to the product being introduced into the supply chain. Despite the industry rules and regulations calling for treat- ment disclosure, the issue often comes down to the ethics and integrity of individual sellers. This presentation discusses some of the commonly encoun- tered treatments and the pricing challenges they present. These include: 1- Dyeing (includes bleaching): Dyeing is achieved by in- troducing a coloring substance such as solvents, chemicals and liquids through pores or fine surface reaching fissures in the stone. In some cases, such as quench crackling, the fissures are created by thermal shock so that the colored liquid can penetrate the stone through the fine breaks. Bleaching should be classified under dyeing, even though it takes away color. It is well known that almost all white pearls go through some level of bleaching. Tahitian choco- late pearls are a result of a propriety bleaching process that turns gray/black pearls into brown. 2- Clarity enhancements: Any gemstone with a surface reaching break has a potential for clarity enhancement. Unlike heat and irradiation treatments, clarity enhancements change the appearance but not the stone’s structure. Almost all fillers are unstable and can be removed. One exception is the flux healing of fractures in corundum which is permanent. Regard- less of the filler and its durability, the level of treatment has an impact on the value. Some of the major international lab- oratories quantify the enhancement in general terms, as well as identity the type of filler in their reports. 3- Coating: A thin film is applied on the surface of a gem in order to modify the color, luster or brilliance. The coating may be applied to part or all of the stone’s surface. Typically, however, the coating is applied to the pavilion. Modern coat- ing techniques are more sophisticated and claimed to be more stable. Colored and iridescent coatings seem to be popular with quartz, beryl and topaz. Coatings have more recently accounted for some of the “fancy” color diamonds in the market; especially of smaller sizes. Coated moissanite is also reported. Coatings are very shallow modifications that create a watery look on the surface. Due to low dura- bility, it is possible to see shallow damages on the color coating that does not go into the stone. 4- Irradiation: This treatment technique is achieved by sub- jecting gems to radiation caused by a variety of energy sources such as X-ray or different energy particles, i.e., neutrons. The major purpose for irradiation is color modification. Most irradi- ation is followed by annealing (heating) to stabilize the effect PRICING WHAT NATURE NEVER INTENDED Çi ˘gdem Lüle, PhD., FGA, GIA GG, DGA, Stuart Robertson, BA, GIA GG PRICING WHAT NATURE NEVER INTENDED ABSTRACT PHOTO 1: Coated diamonds. Photo by Gary Roskin.