Diamantaires often speak of “the life” of a diamond. What gives a diamond life? What exactly is the essence of this life? American Gem Society (AGS) Laboratories’ research and development team decided to answer the question as part of their ongoing study of light performance. Their findings provided surprising results. In short, the answer to the question “What gives a diamond life?” is that diamonds come alive when they sparkle. Light dances across the crown as the stone is rocked back and forth. The stone becomes a complex mosaic of bright white flashes and intense color. The essence of that life is a diamond’s scintillation; it is scintillation that catches the eye and gives diamonds the “wow” factor.
By definition, scintillation is a dynamic characteristic, literally. It needs movement, unlike brightness and fire, which can be assessed and appreciated when the diamond is in a fixed location. Technically, this provides many challenges for researchers seeking to understand scintillation’s mysteries.
THE ESSENCE OF SCINTILLATIONBy virtue of its light performance research, AGS Laboratories has an intense appreciation of scintillation. One of the primary aims of the AGS Laboratories’ research team was to use models that capture the essential elements of what is observed by the eye. The goal was to be practical and realistic. If the eye can’t see it, then why model it? Therefore, the AGS Laboratories’ approach was to first identify the essential elements of the phenomenon being observed and then develop models to explain, simulate and quantify the phenomenon.
One of the primary findings of the research revolves around a simple concept: sparkles. They are the building blocks of scintillation and can be white or colored, few or many. They can be well-distributed across the crown of the stone or localized in certain areas. Sparkles can be large, bold flashes or tiny, infinitesimal slivers. Moreover, different shapes and sizes of sparkles can occur on different parts of the stone. Oval brilliants, for example, frequently have a “cracked glass” appearance near the outer regions, while sparkles near the center — in the bow-tie region — are large and chunky. The pattern of sparkles can change quickly as the stone is moved, or the pattern can change slowly.
A technical term that is useful for discussing sparkles is “virtual facet.” If a diamond’s appearance can be compared to a mosaic pattern of light, then each tile comprising the mosaic is a virtual facet. Each virtual facet is like a tiny window into a specific area of the observer’s environment. A sparkle, then, is a virtual facet that is significantly brighter than the neighboring virtual facets. In general, the more facets in the stone’s facet arrangement, the more the virtual facet pattern is broken into smaller pieces. This is why cutters typically add facets to many traditional designs in order to create a more scintillating stone. This strategy, however, comes with a price; the more subdivided the virtual facet pattern becomes, the fewer large, striking virtual facets remain.
THE RIGHT STUFFNear the end of 2006, the AGS research team began developing the necessary tools to model and quantify scintillation. Like the research that was performed for brilliance and fire, custom ray tracing software was developed to model and study scintillation. Because scintillation is dynamic by nature, the software models the stone in hundreds of orientations to simulate how the stone might perform when rocked back and forth. Various animations of the diamond in motion are then produced in order to accurately display the scintillation potential of the stone. When compared to observations of real stones in motion, these animations show a striking similarity.
Because the virtual facet pattern of a stone is so important to modeling scintillation, the AGS Laboratories’ research software computes critical data about every virtual facet comprising the pattern. This data includes the size, location, source location and dispersion of every virtual facet in the pattern. This data is then used to generate color-coded maps and animations of the stone to illustrate the most important scintillation characteristics that contribute to the overall appearance of the stone. One such map is color coded according to the size of the virtual facets. This particular map is a powerful tool for predicting how the diamond will appear in a variety of lighting environments. These maps clearly illustrate the regions of the stone where one will likely observe large bold “sparkles,” as well as areas that may have a “cracked glass” appearance due to a high concentration of tiny sparkles. Therefore, these maps, as well as others that have been developed, offer a practical tool for evaluating both the quality and quantity of scintillation that may be observed in a diamond.
IMPACT OF SCINTILLATION AT THE SALES COUNTERA deeper understanding of scintillation may enable retailers to better serve their clients’ needs. This is especially true when a consumer is trying to decide between various fancy shapes. As most jewelers are already aware, some diamond cuts tend to “sparkle” more than other facet arrangements. This is because the particular geometry of each cut design subdivides the crown of the stone into a virtual facet pattern common for the particular facet arrangement.
Consequently, some fancy shapes tend to have significantly more virtual facets than other facet arrangements, including the standard round brilliant. Therefore, these stones tend to have more sparkles than other fancy shapes and for some consumers may be more appealing. However, just because a stone has a higher quantity of sparkles doesn’t imply that it is better. There’s a trade-off involved. In general, the more virtual facets on the stone, the smaller they will be. Although stones with a plethora of small virtual facets may appear more sparkly, they will not exhibit the big, bold flashes of light and color as observed in other popular shapes such as the old miner’s cut.
Who’s to say which look is better? It’s a matter of taste. However, armed with the tools and knowledge that AGS Laboratories is in the process of developing, a retailer may be able to help clients make the best choice according to their particular tastes. Informed retailers may be able to use the research to increase their understanding of the underlying mechanisms of scintillation. The more informed the retailer, the better they can help serve their clients at the sales counter. It’s a win-win for the industry and the consumer.
Article from the Rapaport Magazine - February 2008. To subscribe click here.