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There is new excitement in the gem-stone industry. Today, for the first time, scientific advances are
allowing the detailed optical design, precision cutting and characterization metrology of beautiful jewels. Understanding how to cut a stone to best disperse and break light into a plurality of colorful
scintillations has consistently been a major focus of the gemstone industry. Diamonds, for example, are marketed on the basis of the Four C’s: cut, color, clarity and carat weight. Of these four attributes, "cut" is the least understood by the general public and by jewelry industry professionals. The word is used to refer not only to the shape of the diamond but also to its
proportions, symmetry and polish. The quality of the cut is primarily responsible for making a stone appear brilliant and
colorful, or dull and lifeless. It is obvious that an understanding of how a gem manipulates light to produce the effects of brilliance (brightness), fire
(dispersion) and scintillation (sparkle) is critical to the proper design of jewels.
Another important reason to understand the behavior of light in gemstones
is to establish and apply grading systems.* Given the large variety of gem
materials and shapes available today, grading systems that make use of
metrics based on light response and beauty have been introduced. The
gem-buying
public also benefits from an understanding of light propagation in gemstones. The main focus of this article
is to describe the role of optics in gem-stone design along with related
trends in the gemstone industry.
* Professional organizations such as the American
Gem Society (AGS) offer their members services that range from certifying
the authenticity of gems to giving an expert opinion on quality.
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