RAPAPORT... Switzerland's Gübelin Gem Lab has launched a scoring system for colored gemstones based on wine ratings, claiming that the industry lacked a common method of describing quality and uniqueness.
The numerical scale takes into account three factors: quality, rarity and salience — referring to the stone's ability to "stand out from the crowd," Gübelin said last week. Stones will receive a score out of 100, with only those achieving 75 receiving a formal rating.
"So far, there was no common language to uniformly assess colored gemstones," the laboratory said. "Now the Gübelin Gemstone Rating offers orientation, more transparent information, and comparability for final customers as well as the entire industry."
Quality is the key factor, taking into account color, clarity or transparency, and cut. Rarity includes the type of gemstone, its weight, and any treatments. Salience describes the stone's uniqueness.
Gübelin will rate stones as "exceptional" if they receive 97.5 to 100 points. The "outstanding" label is for 95 to 97.4 points, while "excellent" refers to goods achieving 92.5 to 94.9 points. "Superior" covers 90 to 92.4 points, "fine" refers to 85 to 89.9 points, "good" encompasses 80 to 84.9 points, and "fair" is for those scoring between 75 and 79.9.
The lab developed the system for natural stones including rubies, sapphires, emeralds, padparadscha sapphires, paraiba tourmalines, and spinels. Ratings are currently available from Gübelin's Lucerne laboratory.
Image: Rating a gemstone. (Gübelin Gem Lab)
Tags: colored gemstones, grading, Gübelin, Gübelin Gem Lab, Padparadscha sapphires, paraiba tourmalines, Rapaport News, rubies, spinels, Switzerland
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