Looking radiant
Gaining their color from natural radiation, green diamonds are extremely rare and eminently desirable.
Of every 10,000 diamonds discovered, only one is green. These rare diamonds acquire their color after their journey to the earth’s mantle, where they rest in the ground close to natural radiation. This radiation causes defects in the crystal structure of the diamond, leading to absorption of the red and yellow regions of the color spectrum. This is how the stone shows its striking shade of green.
There are several locations, including Brazil, South Africa, Venezuela, Sierra Leone and India, that have a diamond-bearing deposit and where naturally occurring radioactive minerals are found.
“The color of a naturally colored green diamond tends to be confined to the crystal’s outer surface. It occurs as a thin green skin or as patches of green color. On very rare occasions, a natural green diamond may have an even skin coloration throughout,” says Harsh Maheshwari, executive director at Kunming, a Hong Kong-based trading house specializing in natural diamonds.
A radiant-cut, 2-carat, fancy green diamond. Photo: Kunming Diamonds.
Skin deep
Stones that were exposed to a weaker level of radiation tend to lose their green hue during the cutting process. Therefore, manufacturers will usually leave a small amount of the color on the surface to allow grading laboratories to determine a diamond’s natural origin.
“A ‘natural’ unpolished surface of the gem provides proof that the green stain was once a part of the original skin, thus providing positive evidence that the stone is natural. Otherwise, gemologists must resort to alternate means of determining the origin of color, in case of any man-made treatment being involved,” Maheshwari adds.
A green diamond’s color grade is based on the color of the stone and the color intensity level. The Gemological Institute of America (GIA) grades green diamonds on the following scale: faint green, very light green, light green, fancy-light green, fancy green, fancy-intense green, fancy-vivid green and fancy-deep green.
“There can be secondary color modifiers present in a green diamond such as yellow, brown, grey, and in rare instances, even blue color. Green diamonds with no modifications to the color are extremely rare. However, some green diamonds with modifiers are also very rare and hence desirable; for example, a round, vivid-greenish blue over one carat may only be seen once in a lifetime and command a premium,” says David Shara, CEO at New York-based diamond dealer Optimum Diamonds.
Diamonds are treated for two reasons — to improve clarity or to alter the color. The use of advanced technologies to treat diamonds makes it extremely difficult to detect those stones in a grading lab.
“The main problem faced by the industry is that the same structural alteration that may occur in nature over millions of years can be mimicked in the laboratory by man-made treatments; hence determining whether the color of a green diamond comes from nature or the lab is one of the biggest challenges in our industry,” notes Shara.
This makes it essential for diamond collectors to demand that their precious gems come with a grading analysis and origin report.
Optimum Diamonds ring set with a 3.88-carat, vivid-green diamond.
HISTORICAL GREEN DIAMONDS
The Dresden Green
An article in a London newspaper dated October 1722 reports that local diamond merchant Marcus Moses sourced the 41-carat stone from India and presented it to King George I of Great Britain. It was offered a few years later to Frederick Augustus I, elector, and later king, of Saxony. He was a noted collector who created the Green Vault at Dresden Castle for the storage of his jewelry collection.
In 1741, Friedrich Augustus II, king of Saxony, bought the diamond from a Dutch merchant at the Great Annual Easter Fair at Leipzig and in 1768, the diamond was set into a hat ornament with two large, colorless diamonds, and many smaller stones. This is the setting in which the Dresden Green still appears today. It is displayed at the Green Vault.
The Dresden Green.
The Aurora Green
At 5.03 carats, it is the largest vivid-green diamond ever sold at auction, setting a new record price per carat of $3.3 million. It was purchased by the Hong Kong-based jewelry chain Chow Tai Fook for a total of $16.8 million at Christie’s Hong Kong in May 2016.
The Aurora Green. Photo: Christie’s.
Main photo: A cushion, 1.70-carat, fancy intense green diamond. Photo: Kunming Diamonds.
