National Museum of Natural History Gold Colored Diamonds

Brown diamonds are the most common color variety of natural

diamond Diamond is a Allotropes of carbon, solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Diamond is tasteless, odourless, strong, brittle solid, colourless in pure form, a poor conductor of e ...

s. In most mines, brown diamonds account for 15% of production. The brown color makes them less attractive to some people as gemstones, and most are used for industrial purposes. However, improved marketing programs, especially in Australia and the United States, have resulted in brown diamonds becoming valued as gemstones and even referred to as chocolate diamonds. A significant portion of the output of Australian diamond mines is brown stones. There are several causes for the brown color, including irradiation treatment,

nickel Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...

impurities and lattice defects associated with plastic deformation; the last is the predominant cause, especially in pure diamonds. A high-pressure high-temperature treatment can heal lattice defects and convert brown diamonds into yellow or even colorless stones.

Rise in popularity

In 1986, massive amounts of brown diamonds were brought to the market. Rio Tinto opened the Argyle mine in Australia, in which 80% of the diamonds mined were brown in color.

DeBeers The De Beers Group is a South African–British corporation that specializes in the diamond industry, including mining, exploitation, retail, inscription, grading, trading and industrial diamond manufacturing. The company is active in open-pi ...

followed this trend and in 1996 introduced massive number of brown diamonds to the market. These brown diamonds were previously used only for industrial purposes. The value of brown diamonds was hard to determine since the

GIA ''Gia'' is a 1998 American biographical drama television film about the life and times of one of the first supermodels, Gia Carangi. The film stars Angelina Jolie as Gia and Faye Dunaway as Wilhelmina Cooper, with Mercedes Ruehl and Elizab ...

and other third party assessors did not evaluate these diamonds. To rectify the issue, Rio Tinto created a grading system where C1 represents the lightest color and C7 the darkest. In 2000, the fine jewelry company Le Vian trademarked the term "chocolate diamond" and introduced a new brown jewelry line. Le Vian worked with the supplier Rio Tinto and partnered with the retailer, Signet Jewelers. The brand heavily advertised the 'chocolate diamond' line including a massive TV media spend. The campaign was a success; in 2007 virtually no one was searching for "chocolate diamonds", and in 2014 the number jumped to 400,000 times a year.

Occurrence

Raw light brown diamond crystal cut in half - compilation 1

Diamonds occur in various colors, including blue, yellow, green, orange, various shades of pink and red, brown, gray and black. Before the development of the

Argyle diamond mine The Argyle Diamond Mine was a diamond mine located in the East Kimberley region in the remote north of Western Australia. Argyle was at times the largest diamond producer in the world by volume (14 million carats in 2018), although the propo ...

in Australia in 1986, most brown diamonds were considered worthless for jewelry; they were not even assessed on the

diamond color A chemically pure and structurally perfect diamond (gemstone), diamond is perfectly transparent with no hue, or color. However, in reality almost no gem-sized natural diamonds are absolutely perfect. The color of a diamond may be affected by colo ...

scale, and were predominantly used for industrial purposes. However, marketing strategies changed in the 1980s and brown diamonds have become popular gems. The change was mostly due to supply: the Argyle mine, with its 35 million carats (7,000 kg) of diamonds per year, makes about one third of global production of natural diamonds; 80% of Argyle diamonds are brown. The percentage of brown diamonds is lower in other mines, but it is almost always a significant part of the total production. Consequently, scientific research has intensified on causes of brown color in diamond and ways to alter it.

Notable brown diamonds

*The

Golden Jubilee Diamond The Golden Jubilee Diamond, a 545.67 carat (109.13 g) brown diamond, is the largest cut and faceted diamond in the world. It outweighs the Cullinan I by 15.37 carats (3.07 g). The Golden Jubilee Diamond was discovered in 1985 at the Premier Min ...

is the largest cut diamond in the world. It was found in 1985 as a rough stone of 755.5 carats (151 g) in the

Premier Mine The Premier Mine is an underground diamond mine owned by Petra Diamonds in the town of Cullinan, Gauteng, Cullinan, east of Pretoria, Gauteng Province, South Africa. Established in 1902, it was renamed the Cullinan Diamond Mine in November ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

, which is operated by

De Beers The De Beers Group is a South African–British corporation that specializes in the diamond industry, including mining, exploitation, retail, inscription, grading, trading and industrial diamond manufacturing. The company is active in open-pi ...

. The stone was cut into a 545.67-carat (109.13 g) and was purchased from

De Beers The De Beers Group is a South African–British corporation that specializes in the diamond industry, including mining, exploitation, retail, inscription, grading, trading and industrial diamond manufacturing. The company is active in open-pi ...

by a group of businessmen led by Henry Ho of Thailand in 1995. The Golden Jubilee Diamond was named by king

Bhumibol Adulyadej Bhumibol Adulyadej (5 December 192713 October 2016), titled Rama IX, was King of Thailand from 1946 until Death and funeral of Bhumibol Adulyadej, his death in 2016. His reign of 70 years and 126 days is the longest of any List of Thai mo ...

and given to him on occasion of his 50th coronation anniversary. *The Earth Star Diamond was found at another South African mine of

De Beers The De Beers Group is a South African–British corporation that specializes in the diamond industry, including mining, exploitation, retail, inscription, grading, trading and industrial diamond manufacturing. The company is active in open-pi ...

, the

Jagersfontein Mine Jagersfontein Mine was an open-pit mine in South Africa, located close to the town of Jagersfontein and about south-west of Bloemfontein.pear-shaped gem with a strong brown color and extraordinary brilliance. The diamond was bought in 1983 for $900,000. *The

Star of the South The Star of the South, also known as 'Limar', is a diamond found in Brazil in July 1853. The diamond is cut into a cushion shape and weighs . The Star of the South is graded as a type IIa diamond, with a color grading of fancy light pinkish-b ...

(the original name was Portuguese "Estrela do Sul") is one of the largest diamonds found in Brazil and the first Brazilian diamond to receive international acclaim. The original rough stone was found in 1853 by an enslaved African woman, for which she received her freedom and life pension. The diamond was cut into a cushion shaped gem weighing . For a long time, the Star of the South was considered to be "by far the largest diamond discovered by any woman anywhere", until the Incomparable Diamond was discovered in the 1980s. The diamond has a color grade of Fancy Light Pinkish-Brown. *The Incomparable Diamond is another African diamond, one of the largest ever found in the world (). In 1984, a young girl discovered it in a pile of rubble from old mine dumps of the nearby MIBA Diamond Mine,

Democratic Republic of the Congo The Democratic Republic of the Congo (DRC), also known as the DR Congo, Congo-Kinshasa, or simply the Congo (the last ambiguously also referring to the neighbouring Republic of the Congo), is a country in Central Africa. By land area, it is t ...

. The rubble had been discarded during the recovery process because it had been considered too bulky to contain diamonds. Before cutting, the stone was the largest brown diamond and the fourth largest diamond of any color ever discovered after the Cullinan (),

Excelsior Diamond The Excelsior Diamond is a gem-quality diamond, and was the largest known diamond in the world from the time of its discovery in 1893 until 1905, when the Cullinan Diamond was found. It was found on June 30, 1893, at the Jagersfontein Mine in S ...

() and

Star of Sierra Leone The Star of Sierra Leone diamond was discovered by miners on February 14, 1972, in the Diminco alluvial mines in the Koidu area of Sierra Leone. It ranks as the fourth-largest gem-quality diamond and the largest alluvial diamond ever discovered. ...

(). The massive diamond's owners initially planned to cut it into the world's largest gem. However, the diamond's final size was reduced to in order to reduce the number of internal flaws. Nevertheless, it was the 3rd largest cut diamond after the Cullinan I and

s. The stone was cut by a team led by Marvin Samuels, who co-owned the stone along with Donald Zale of Zales Jewellers and Louis Glick. In November 1984 the finished stones were put on display: a single golden diamond of in a ' triolette' shape, and fourteen additional gems. Notably, the satellite stones cut from the Incomparable varied greatly in color, from near-colorless to rich yellow-brown. The largest of these stones still bears the name 'Incomparable Diamond', and was graded by the

as internally flawless in 1988. In December 2000, jeweler Leland McKee entered into a master agreement to offer The Incomparable Diamond at auction on the eBay website for $26,500,000.00. The auction ended with no sale and is still considered the most expensive loose diamond ever offered and listed on the eBay auction site. The intended sale is referenced on various websites under The Incomparable Diamond. *The Lesotho Brown was unearthed at the

Letseng diamond mine The Letšeng Diamond Mine, found in the landlocked Southern African kingdom of Lesotho, is owned by Gem Diamonds, Ltd. and the government of Lesotho, at an elevation of it is the world's highest diamond mine. Production It is characterised ...

Lesotho Lesotho, formally the Kingdom of Lesotho and formerly known as Basutoland, is a landlocked country in Southern Africa. Entirely surrounded by South Africa, it is the largest of only three sovereign enclave and exclave, enclaves in the world, t ...

in 1967 at Letseng-la-Terai by Ernestine Ramaboa. The rough stone weighed and was cut in 1968 into 18 polished diamonds totaling . The largest was a emerald cut known as the Lesotho I. The Lesotho III (the third largest stone cut from the crystal) is a marquise-shaped gem that was once owned by

Jacqueline Kennedy Onassis Jacqueline Lee Kennedy Onassis ( ; July 28, 1929 – May 19, 1994) was an American writer, book editor, and socialite who served as the first lady of the United States from 1961 to 1963, as the wife of President John F. Kennedy. A popular f ...

, given to her by her husband

Aristotle Onassis Aristotle Socrates Onassis (, ; , ; 20 January 1906 – 15 March 1975) was a Greek and Argentine business magnate. He amassed the world's largest privately-owned shipping fleet and was one of the world's richest and most famous men. He was marri ...

as an engagement ring. It was mounted in a platinum ring created by

Harry Winston Harry Winston (né Weinstein; March 1, 1896December 8, 1978) was an American jeweler. He donated the Hope Diamond to the Smithsonian Institution in 1958 after owning it for a decade. He also traded the Portuguese Diamond to the Smithsonian in ...

. The ring had an estimated value of $600,000 US, but at the Jackie Kennedy estate sale auction in April 1996 it reached a price of $2,587,500 US dollars. The Lesotho I was offered at

Sotheby's Sotheby's ( ) is a British-founded multinational corporation with headquarters in New York City. It is one of the world's largest brokers of fine art, fine and decorative art, jewellery, and collectibles. It has 80 locations in 40 countries, an ...

, Geneva on November 19, 2008 as part of a Magnificent Jewels sale, but it did not sell. Its value was estimated before the sale to be 3,360,000 to 5,600,000

Swiss franc The Swiss franc, or simply the franc, is the currency and legal tender of Switzerland and Liechtenstein. It is also legal tender in the Italian exclave of Campione d'Italia which is surrounded by Swiss territory. The Swiss National Bank (SNB) iss ...

s, which equated to $2,783,894 to $4,639,824 US dollars. The lot's description mentioned it was being offered for sale by the same owner who had originally bought it from Harry Winston around 1969. It also listed the gem as having a clarity of VVS2, excellent polish and excellent symmetry, and, although the stone (and the other Lesotho fragments) is a pale brown color, no color grade is mentioned in the auction text. *In 1974, Elizabeth Taylor wore a cognac diamond ring and earrings to the Oscars. The jewelry was a gift from Richard Burton for their tenth anniversary.

Causes of color

Irradiation

Irradiation of diamond by high-energy particles (

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

neutron The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...

s or

gamma ray A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...

s) produces vacancies in the diamond lattice by ejecting carbon atoms. Those vacancies produce green color centers in pure transparent diamond and yellow-green color in yellow diamonds. The color of yellow diamonds results from small numbers of nitrogen atoms replacing carbon in the lattice. Heating the irradiated diamonds to temperatures above 600 °C results in brown color associated with aggregation of the vacancies, with or without nitrogen involved. Such irradiation and annealing treatment can occur in nature because diamonds are often accompanied by uranium-containing ores which emit alpha particles. However, the thus produced color is restricted to a thin surface layer of few micrometers. Homogeneous color can be produced if the treatment is performed artificially, using electrons, neutrons or gamma-rays. Radiation treatment induces characteristic sharp optical absorption lines which can be easily detected by spectroscopic techniques.

Brown synthetic diamonds

Synthetic diamonds created by compressing graphite to several gigapascals and heating to temperatures above 1500 °C are usually rich in nitrogen. Nitrogen in those diamonds is dispersed through the lattice as single atoms and induces yellow color. Nickel is often added to graphite to accelerate its conversion into diamond. Incorporation of nickel and nitrogen into diamond induces brown color. Nickel is easily detectable by characteristic, sharp optical absorption and luminescence signals making such diamonds easily identifiable.

Natural brown diamonds

Whereas the brown color due to irradiation or nickel impurity can be easily recognized through spectroscopic (e.g. absorption) measurements, the majority of natural brown diamonds do not show any characteristic absorption peaks. Whereas the consensus has been reached that the color relates to the plastic deformation, the particular reason has been reliably identified (large clusters of vacancies) only in type IIa natural brown diamond. Other recent results suggest that these large clusters of vacancies (mini-voids) are a likely cause in other types of diamond as well. Those lattice defects are most likely responsible for the color of the notable diamonds described above.

Heat-treated brown diamonds

The concept that brown color might be related to lattice imperfections has led to a technique to convert brown diamonds into more valued light-yellow or even colorless ones: the diamond is subjected to high pressures of 6–10 GPa and temperatures above 1600 °C that heals (anneals) those defects. The technique has been demonstrated in several research laboratories in Russia and the United States. In March 1999, Pegasus Overseas Ltd (POL) from

Antwerp Antwerp (; ; ) is a City status in Belgium, city and a Municipalities of Belgium, municipality in the Flemish Region of Belgium. It is the capital and largest city of Antwerp Province, and the third-largest city in Belgium by area at , after ...

Belgium Belgium, officially the Kingdom of Belgium, is a country in Northwestern Europe. Situated in a coastal lowland region known as the Low Countries, it is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeas ...

, a subsidiary of

Lazare Kaplan International Lazare Kaplan International Inc. (LKI) is a diamond manufacturing and distribution company based in New York City. The Chairman of the Board of Directors is Maurice Tempelsman. The first LKI was located in Ponce, Puerto Rico, at , a community nam ...

, started marketing such diamonds that were processed by

General Electric General Electric Company (GE) was an American Multinational corporation, multinational Conglomerate (company), conglomerate founded in 1892, incorporated in the New York (state), state of New York and headquartered in Boston. Over the year ...

(GE). Those diamonds therefore received the name GE POL (or GEPOL) and were marketed in the US as ''Bellataire'' diamonds. The existence and identity of the treatment process was considered so important that micrometer-sized letters "GEPOL" were inscribed with a laser on the

girdles A belt without a buckle, especially if a cord or rope, is called a girdle in various contexts, especially historical ones, where girdles were a very common part of everyday clothing from antiquity until perhaps the 15th century, especially for w ...

of every treated diamond. In 2004, however, the GE diamond section was purchased by Littlejohn & Co. and renamed ''Diamond Innovations''. Since 1999, several companies around the world have adopted the technique and use various

brand name A brand is a name, term, design, symbol or any other feature that distinguishes one seller's goods or service from those of other sellers. Brands are used in business, marketing, and advertising for recognition and, importantly, to create and ...

s for the processed diamonds.

References

{{DEFAULTSORT:Brown Diamonds Diamond colors

Rise in popularity

Occurrence

Notable brown diamonds

Causes of color

Irradiation

Brown synthetic diamonds

Natural brown diamonds

Heat-treated brown diamonds

See also

References