Jim Shigley

Country-of-Origin Determination in Colored Gemstones

What would you do if you stumbled across a beautiful, perfectly faceted sapphire? The kind that glistens in the light like a dancing fire, that gives a thousand perfect reflections, that tells a story of wonder and mystique. It's a rich royal blue, only slightly bigger than the size of a pea. What value could such a treasure hold?

Dr. James Shigley favored students with a presentation titled "Country-of-Origin Determination in Colored Gemstones (but not for Diamonds)" at the February 27, 2025 seminar hosted by the BYU Department of Geological Sciences. Dr. Shigley is one of the foremost experts in gemology in the world, boasting a distinguished career spanning dozens of countries and countless discoveries. He is a graduate of the University of California, Berkeley, and has a doctorate in geology from Stanford University. He served honorably in the U.S. Army from 1971 to 1976, retiring from the Army Reserve as a lieutenant colonel. He joined the Gemological Institute of America (GIA), one of the most prominent gemology facilities in the country, as a senior research scientist, where he has worked ever since. He is currently GIA's director of research and the Institute's first and only distinguished research fellow.

The lecture was on the process by which the origins of gemstones are determined, why that matters, and why the process doesn't work for diamonds. Dr. Shigley explained that in the gem industry, much of the value of a gemstone comes from the country of its origin, often because of its rarity or, in some cases, its supposed mystical properties. Many gemstones are sought out specifically for this reason. An example of this is the sapphires of Kashmir, which are the most valuable sapphires in the world due to their incredible rarity and legendary status as the standard for gemstone opulence. GIA Institute is dedicated to identifying the origins of gemstones based on their color, appearance, and chemical compositions, cross-referencing with their vast collection of tens of thousands of gems and extensive worldwide database. Gemstones of the same location will often have the same or similar characteristics. Thus, by examining these traits, they are able to compare them with other gems on record from the numerous mining locations around the world. They use various tools to accomplish this goal, including microscopy, using microscopes to look at the structures of the gems, and spectroscopy, looking at the levels of light absorbed by the gems. These techniques, when compared with the institute's data, show researchers like Dr. Shigley where the gem may have originated.

Unlike sapphires, rubies, or emeralds, diamonds are much more difficult to trace for many different reasons. For one, diamonds mostly form in similar geological environments in the earth's mantle and therefore do not have any identifiable unique crustal characteristics, unlike most other gemstones. They form under immense pressure hundreds of kilometers below the Earth's surface and are then brought close to the surface as a result of volcanic eruptions that occurred millions of years ago. They are then either deposited in the remains of these eruptions, called kimberlite pipes, or are carried away in rivers, making it incredibly difficult to accurately differentiate the diamond's country of origin. Scientists will often use trace elements that can be found within the composition of gemstones to help identify what other compositions those gems most closely match. However, the concentration of trace elements in diamonds can be up to one thousand times lower than what is found in other gemstones. These factors have led to a different value rating system for diamonds called the 4 Cs (cut, color, clarity, and carat), which does not include country of origin. This means that databases and information regarding where diamonds come from are severely lacking, making it difficult to do any sort of cross-referencing. With that being said, GIA has had some success in creating tracking reports for the diamonds that are brought to them.

They do this by examining and cataloging uncut diamonds from known locations, then recording the diamonds as they appear after being cut and shaped. This doesn't necessarily mean that the diamonds actually originated from the matched location, as there is no real scientific way to prove it, but it does give researchers a better idea.

You're in luck! With the help of Dr. Shigley and his colleagues, you're able to identify where your little sapphire came from: the legendary mines of Kashmir. And now you're rich!

If you would like to learn more about diamonds and other gems or explore invaluable educational and career opportunities, visit GIA.edu.