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Green Diamonds

One of the rarest and most valuable diamond colors

green diamonds

Author: , Ph.D., GIA Graduate Gemologist

Green Diamond: This green diamond has all of the characteristics of a highly desirable colored diamond: A) it is a natural diamond; B) the green color was produced by nature; and, C) the color is a pure green with a rich saturation. The Gemological Institute of America graded its color as “fancy vivid green” with a natural origin and an even distribution.

Have You Seen a Green Diamond?

Green diamonds are very rare. Of all diamonds cut into polished gems in any given year, a very small number of them will have a dominant green color. Green diamonds are rare enough that many people have never seen one, and those who have seen one are likely to have seen it in a museum exhibit.

You are unlikely to find a green diamond in a mall jewelry store. But even though green diamonds are extremely rare, there are a few companies who have a long history in the retail colored diamonds business. So, anyone who wants a green diamond and can afford one should be able to find a selection of green diamonds to consider.

Natural Green Color in Diamonds

In many green diamonds, the color is confined to a thin layer at the surface of the rough stone. The design and cut of the polished diamond must be carefully planned and executed to conserve as much of that original color as possible. Even though the faceting might only preserve a band of green color around the girdle and a small amount in the culet, that can be enough to produce an apparent green color throughout the stone. These diamonds often display a green color which is very subtle.

Most green diamonds have a color that is modified by hints of yellow, blue, or gray. Variations in color, tone, and saturation can make a big difference in the selling price of the gem. The most valuable green diamonds have a pure green color, medium tone, and strong saturation. These richly colored diamonds might earn a color grade of “fancy intense” or “fancy vivid.” Such gems are exceedingly rare and will fetch premium prices.

What Causes the Color of Green Diamonds?

A) Natural Green Diamonds

Diamonds with a natural green color most likely developed that color while they were underground, in rocks that contained small amounts of radioactive material such as uranium or thorium. As the radioactive materials decayed, they emitted radiation that penetrated the nearby diamond crystal. When this type of radiation enters a diamond, it can knock electrons or carbon atoms out of their position in the crystal lattice.

The displacement of electrons and carbon atoms deforms the crystal lattice and changes the way light travels through the diamond. The deformation causes the diamond crystal to selectively absorb much of the light entering the diamond and selectively transmit wavelengths in the green portion of the spectrum. This green light travels to the eye of the observer and gives the diamond a green appearance.

B) Treated Green Diamonds

Ingenious people are always trying improve the color of gemstones to increase their value. They do this by mimicking the processes of nature or applying treatments that alter the color of the gem.

The first documented treatment to produce green diamonds was an experiment done by Antoine-Henri Becquerel, shortly after his discovery of radioactivity in 1896. He irradiated some diamonds to see if they would be altered, and their color changed to green.

In 1904, Sir William Crookes stored a few polished diamonds in radioactive salts. When they were removed from the salt, the diamonds had a green color at the surface and that color extended to a shallow depth. This method of diamond treatment is not used today because the diamonds can be contaminated with radioactivity that does not decay to safe levels within a reasonable period of time.

The most common laboratory treatment used today to produce a green color in diamonds is irradiation of polished diamonds with a low-energy electron beam. This treatment can modify near-colorless or yellow diamonds to produce diamonds with a green color.

Another treatment to produce green diamonds today is to apply a thin coating of silica to the surface of the polished gems. The coating can produce an attractive appearance, but it is very thin and can eventually be worn off by the abrasion of normal wear.

Diamonds that owe their green color to a treatment should always be sold with a disclosure that the color was produced by treatment, and state the method of treatment. Because so many buyers prefer diamonds with a natural color, green diamonds colored by treatment generally sell for a significantly lower price than natural green diamonds of similar color, size and quality.

A Synthetic Diamond Treated to Produce a Fancy Deep Blue-Green Color: The blue-green synthetic diamond above had an “as-grown” Fancy Intense Orange Yellow color, then post-growth irradiation and annealing treatments transformed it into a Fancy Deep Blue-Green color.

C) Green Synthetic Diamonds

Synthetic diamond crystals have been successfully grown in laboratories in a variety of colors. Synthetic diamonds with a light green color and a greenish yellow color have been produced when small amounts of nitrogen and boron were incorporated into the diamond.

Green synthetic diamonds have also been produced by irradiating colorless or yellow synthetic diamonds. So, there can be green synthetic diamonds with an “as grown” green color, and green synthetic diamonds that obtained their green color from “post-growth treatments.”

Are Irradiated Diamonds Safe?

Because many green diamonds obtain their color from exposure to radiation in a laboratory (a process known as irradiation), there have been concerns about their safety when used in jewelry.

All companies in the United States that apply radiation treatments to any type of gemstone must be licensed by the Nuclear Regulatory Commission. These companies must use approved methods to treat the gemstones, then store them in a secure facility until their radioactivity declines below a level that would make them safe for use in jewelry. Only then can they be released for jewelry manufacturing or sale to the public.

The process of gemstone irradiation is very common. Almost all of the blue topaz offered in stores today is colorless topaz that has been irradiated and then heated to produce a blue color. “Swiss blue” and “London blue” are trade names for two of the most common varieties of treated blue topaz seen in today’s market.

Gemstones have been treated by irradiation in the United States for decades with the Nuclear Regulatory Commission actively licensing companies who do the treatments. Based upon their experience the NRC reports:

The NRC has no reason to believe that wearing irradiated gemstones can be harmful. There have been no reported cases of anyone being harmed by wearing them. There is no safety reason to stop wearing blue topaz or any other irradiated gems. [5]

Famous Green Diamonds

Aurora green diamond
The Aurora Green Diamond

The “Aurora Green” Diamond: This ring, holding the 5.03-carat Aurora Green diamond, surrounded by circular-cut pink diamonds was sold at auction by Christie’s in 2016 for $16.2 million. It holds two important distinctions: A) the highest price ever paid for a green diamond at auction; B) the largest natural color, fancy vivid green diamond ever graded by the Gemological Institute of America.

Two of the most famous and valuable green diamonds are the “Aurora Green” and the “Dresden Green.”

In 2016, a ring containing the Aurora Green, a 5.03-carat, VS2 clarity, fancy vivid green diamond, was sold at a Christie’s auction for $16.2 million. That was the highest price ever paid for a green diamond at public auction.

Prior to the auction, gemologists at the Gemological Institute of America graded the Aurora Green and reported that it was the largest fancy vivid green diamond with a natural color that they had ever graded as of January 20, 2016.

The Dresden Green Diamond
The Dresden Green Diamond

The “Dresden Green” Diamond: A glass copy of the famous Dresden Grün from the “Reich der Kristalle” museum in Munich.  The Dresden Green is a natural green Type IIa diamond with a clarity grade of VS1. It is a faceted gem of 41 carats with a uniform green color. Some diamond experts believe that it was cut from a rough diamond produced at the Kollur Mine in the Indian State of Andhra Pradesh. Others believe that it was cut from rough mined in Brazil. [1] The first known record of the Dresden Green is from a 1772 article in a London newspaper. The date of this article corresponds to a time when a number of green diamonds with uniform color were mined in Brazil and brought to Europe.

The Challenge of Cutting Green Diamonds

Most green diamonds have a color that is only “skin deep.” This prevents many of them from being cut into faceted gems that retain a distinct green color. Diamonds with a green color that is evenly distributed through the stone are exceptionally rare.

When the green color is confined to a thin layer just below the natural surface of the rough, the shape of the finished diamond must be carefully planned to preserve as much green color as possible. Often the diamond is cut to preserve green color around the girdle of the stone or sometimes to preserve color in the culet. With a small volume of color to start and sometimes only a portion of it remaining, these green diamonds are a special challenge to cut and often have a low color saturation.

 

Green Diamond Information
1. The Nature of Diamonds: by George E. Harlow; a book published by Cambridge University Press in association with the American Museum of Natural History; 278 pages; 1998.

2. Green Diamond: Treated by Radioactive Salt: by Marzena Nazz and Paul Johnson; Gems & Gemology; Spring 2013.

3. Diamonds and Color: Gemological Institute of America; Chapter 12; Diamonds & Diamond Grading course materials; page 13. Revised 2014 edition.

 

Determining the Origin of Green Color

Anyone who contemplates spending significant money on a green diamond should purchase the diamond from a business that has a reputation for selling colored diamonds. In addition, the diamond and the cause of its color should be authenticated by a trusted laboratory.

“Origin of color” is an assessment that some diamond grading laboratories include on a diamond identification report for a colored diamond. If you are purchasing a colored diamond, look for “origin of color” on the report.

Some gemological laboratories can reliably determine the cause of color in many green diamonds; however, the origin of green color cannot be confidently determined for every diamond. It can be difficult to impossible to separate a naturally irradiated green diamond from a laboratory-irradiated green diamond. In cases where the laboratory is unable to confirm the origin of color they will report that the cause of the color as “unknown” or “undetermined.”

When Christie’s sold the Aurora Green, it was submitted for identification and grading to the Gemological Institute of America. The colored diamond grading report prepared by GIA stated the origin and color of the Aurora Green as “natural, fancy vivid green, with an even distribution.”

A grading report from a diamond authority such as GIA can support the confidence and comfort of both buyer and seller. The cost to obtain a lab report from a reputable lab is a tiny fraction of the cost of a nice diamond, making it an excellent investment and insurance policy at the same time.

April Birthstone: Diamond

diamond shapes

A diamond is a stone that truly states, “I love you” in a deep way. In fact, you’ve probably heard the slogan many times that “a diamond is forever.” This is because of the stone’s symbol of deep, everlasting love, as well as the fact that it’s the hardest substance known on earth.The diamond is also the stone that marks the 60th anniversary of marriage, and is the birthstone for the month of April. It is believed that the first diamonds were discovered in India. In Ancient India, people viewed diamonds as religious icons.
Australia-origin-of-diamond.jpg Going back to early history, diamonds were always used to engrave tools because of their hardness. Diamonds have been found all over the world on all continents. In 600 AD, diamonds were found in Borneo, an island located north of Australia. In the 1700’s, Brazil was a rich source of diamonds, and in the 1800’s, South Africa was known for their large supply of diamonds. Since the 1970’s, Australia has been a large source for the precious stones.
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Ancient Greeks named the diamond “adamas,” meaning “invincible,” “indestructible,” “proper,” and “untamed.” Warriors in ancient Greece wore diamonds as the stones were thought to strengthen the warriors’ muscles and bring them invincibility. The power, hardness and beauty of the diamond have been prized throughout history in many civilizations. The famous Persian poet Hafiz remarked that, “the rainbow is confined in a diamond forever”. In antiquity, a diamond was always thought to be a symbol of innocence and purity. Ancient Greeks thought that diamonds represented the tears of weeping gods. Ancient Romans thought diamonds were considered to be parts of the outer rings of stars, which had fallen to the earth.

diamond-history-napolean-strength.jpg Almost every civilization has some kind of lore on the diamond. Every civilization’s lore however, shares one theme- that the diamond symbolizes all forces necessary for a healthy society, and that it brings its wearer great strength. The diamond was always considered a stone of winners. In fact, it was the talisman of Julius Caesar, Louis IV and Napoleon.
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The Renaissance Period was the first point in time when diamonds were used as engagement rings. They were thought to be a special gift, which represented the very ultimate gift of love. In 1477, this trend was started when Archduke Maximillian gave Mary of Burgundy a diamond engagement ring. This was a trend that was only popular among royalty and the very wealthy.

diamonds-facts-jewelry-rings.jpg Giving a diamond as an engagement ring did not actually become a standard until the De Beers marketing campaign started, during the 20th Century. Today, the primary use of diamonds is no longer for carving or protection during battles. They are now used for adornment because of the their sheer beauty- their dispersion of white light into many different beautiful colors, and their brilliance and indestructibility. Gemologists now rate diamonds based upon what is called “the 4 C’s,” referring to carat, cut, color, and clarity.
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“Carat” refers to the weight of the diamond. “Cut” refers to the brilliance of the stone, as the way it is cut determines how much brilliance a diamond will have. “Clarity” refers to the natural blemishes found inside diamonds (and remember, a flawless diamond is extremely rare). Finally, “color” is the last important factor when choosing a diamond. The highest color ranking for a diamond represents a completely clear and colorless stone.

Physical Properties and Science of Diamond

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As the hardest mineral in existence, a diamond is highly regarded for its beauty and ability to reflect light in an extremely dazzling way. Diamonds display a large amount of brilliance and fire, meaning they sparkle a lot, and always retain a freshly polished look.Created out of pure carbon, the carbon atoms within diamonds are bonded very strongly, which makes for the hardness and strength of the stone. Diamonds are the hardest known substances.

durability-diamond-jewelry-birthstone.jpg Because of the strength of this carbon bonding, diamonds rate a 10 on the Mohs scale- meaning they are as hard as a stone could possibly be. Since antiquity, it has been known that diamonds are the hardest stone. Because of this, the hardest diamonds can only be scratched with other diamonds. Also because of their hardness, not too much care is needed to keep your diamond looking new. It keeps a polish for a very long time and is therefore suitable for everyday wear. Other chemicals cannot affect diamonds, because they are the most durable and inert material.
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In their most natural form, diamonds are clear, but because of impurities of light elements, such as nitrogen, diamonds can also be found in colors such as orange, green, blue, pink, black, yellow, orange, green, red, and brown.

diamond-light-refraction-facts.jpg The brilliance of a diamonds comes from a combination of reflection, dispersion, and refraction. A ray of light first passes through a diamond and is then bent, or refracted. Then, this bent ray is reflected through a facet at the bottom of the stone and through the top of the stone. When refraction occurs, each ray is bent at a slightly different angle, which is referred to as dispersion. Of all gems, diamonds have the highest index of refraction.
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The most popular cut of diamond is called a brilliant cut, a cut where numerous facets are placed so the most rays of light will reflect through them. This cut is determined by mathematical and empirical analysis. A Brilliant cut does not refer to the shape of the actual stone, but the proportion and symmetry of the diamond.

 

For more info on diamonds, click on: https://www.gia.edu/diamond

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