In May 2016, two world auction records were set at Christie’s Hong Kong Magnificent Jewels sale in Hong Kong. On the block was a 5.03-carat fancy colored green diamond with VS2 clarity, called the “Aurora Green.” It was mounted on a gold ring, surrounded by 20 circular-cut pink diamonds.
After several minutes of bidding, the item sold for $16.8 million to Chow Tai Fook Jewellery, the Hong Kong-based firm that is one of the world’s two largest jewelry retailers. It shattered the record for fancy colored green diamonds, set just two weeks earlier at Christie’s in Geneva by the Ocean Dream, a 5.5-carat fancy vivid blue-green diamond, which went for $8.6 million. The $3.3 million per carat handed over for the Aurora Green was also the highest ever recorded for a fancy green diamond, more than twice the $1.5 million per carat paid for the Ocean Dream.
Natural fancy green diamonds are exceedingly rare. Ranging in intensity from faint green to intense green, pure green stones are known to exist, but more often the come with one or even two secondary hues, which typically are yellows, blues, browns and grays of different intensities.
The source of the green color in natural stones is their being exposed over millions of years underground to radioactive minerals located in close proximity, such as uranium. The diamonds themselves are not radioactive.
This raises an interesting dilemma, because other diamonds can be irradiated using a linear accelerator, gamma rays or in a nuclear reactor, to artificially create a green diamond. Because radiation occurring in nature is similar to the type of radiation used to treat diamonds, gemological labs sometimes struggle to differentiate between natural and treated color. But researchers at the Gemological Institute of America (GIA) have found some definitive markers that can do the job. Natural green diamonds frequently display green or brown surface spots, called radiation stains, which do not appear in artificially green diamonds. Treated green diamonds usually have their color spread homogenously throughout the stone.
The most famous member of this family is the Dresden Green, which at 41 carats is largest-known natural green diamond in existence. Believed to have been discovered in a diamond mine in the Golconda district in India, it was brought to London in 1726, and was purchased by the king of Poland. It was first set in a specially commissioned badge of the Order of the Golden Fleece, and later in a hat ornament. For more than 200 years the diamond has been kept in a museum in Dresden, Germany, except during times of war when it was moved for safekeeping to a fortress.
Other than its size, what sets the Dresden Green apart from most other natural fancy colored green diamonds is the fact that the green color is spread uniformly throughout the stone. GIA was granted permission to study the stone in order to ascertain the exact origin of its color, but was unable to come up with a definitive finding. It did not, however, question whether it was natural, because the stone was discovered centuries before the earliest known irradiation techniques were developed.
The 25-carat Gruosi Green Diamond is considered to be the world’s second largest known natural fancy green diamond. It has been owned since 1998 by Fawaz Gruosi, owner of the Swiss Jewelry house de Grisogono, who purchased it as a 100-carat rough stone in 1998. Three quarter of its volume was lost during the cutting and polishing process, where the declared intention was to produce the largest possible fancy colored green gem.
The 31.32-carat oval-cut Chopard Chameleon diamond is actually larger, but it not strictly a green diamond because of its ability to change color. Indeed, it is the largest know such diamond. In natural light under normal conditions it displays an olive-green color, but after being kept in the dark for 24 hours, or when it is heated to approximately 200 degrees Celsius, it color shifts to an an intense yellow or orange-yellow hue.
MID House of Diamonds is of the world’s preeminent suppliers of loose fancy-colored diamonds, with a large and varied stock that includes green stones. Because it is a world of which many diamond buyers are less familiar, with different pricing patterns and grading standards, MID invites you to speak with one of the fancy color experts on its team.