Brent D. Johnson, Senior News Editor
Jeweler Pierre Cartier was legendary for spinning yarns about the exotic origins of his collection, associating gems with palace intrigues and religious talismans in far-off lands. His invention of the Hope diamond curse, based on a story by the 18th-century adventurer Jean-Baptiste Tavernier and, less notably, Cartier's sale of a single strand of natural pearls in exchange for a historic New York mansion, helped to secure his reputation as a master of the deal.
Ken Scarratt, director of the gem association's testing center, employs the portable MCS-501 UV-VIS spectrophotometer from Carl Zeiss both in-house and off-site. He said that the device is user-friendly and that portability and speed are important advantages over similar equipment he has used.
Today's sophisticated buyers and sellers need more than a captivating story and a pat on the back to establish the value of a precious gem. In the current marketplace, price is determined by the five C's: color, cut, clarity, carat and country of origin. Naked-eye evaluations and other techniques can determine the first four, but how does one identify the source?
The American Gem Trade Association has developed a technique using UV-VIS and Raman spectroscopy to identify the origins of gemstones. The technique reads the total absorption and compares different spectral peaks, which have a slightly different shape for each mine in most of the important gemological localities.
Ken Scarratt, director of the gem association's testing center, employs the portable MCS-501 UV-VIS spectrophotometer from Carl Zeiss both in-house and off-site. He said that the device is user-friendly and that portability and speed are important advantages over similar equipment he has used.
The machine can collect a sample in just a few minutes vs. 10 to 15 minutes or longer for the nonportable device previously used by the association.
He explained that the price structure of the sapphire is partially dependent on rarity. The stones from Kashmir, India, are beautiful and rare. By contrast, "the sapphires from the mines in New South Wales [Australia] are so abundant you could almost line your garden path with them," he said. They are very dark and, generally, their quality is not very good. In terms of perceived quality and rarity, the pecking order for sapphires is Kashmir, Myanmar, Sri Lanka and Madagascar.
"The price paid for these gems at auction is often related to the country of origin, and this is inevitably given with the stone listing in the auction catalog," Scarratt said. "So establishing the origin is very important to the trade."