Brown diamonds

Brown diamonds are the most common color variety of natural diamonds. In most mines, brown diamonds account for 15% of production. The brown color makes them less attractive as gemstones because of the reduced glimmer, 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 in recent years and even referred to as chocolate diamonds. A significant portion of the output of Australian diamond mines is brown stones. A large amount of scientific research has gone into understanding the origin of the brown color. Several causes have been identified, including irradiation treatment, nickel impurities and lattice defects associated with plastic deformation; the latter is considered as the predominant cause, especially in pure diamonds. A high-pressure high-temperature treatment has been developed that heals lattice defects and converts brown diamonds into yellow or even colorless stones.

Baumgold Bros., a popular diamond cutter and fine jewelry importer in the 1950s and 1960s rebranded brown diamonds in order to entice sales. Names included champagne, amber, cognac, and chocolate. Other companies followed the Baumgold Bros. lead and named different shades clove, coffee, caramel, cappuccino, mocha, espresso, cinnamon and even tobacco. This rebranding has some initial success, but ultimately the massive number of names caused confusion in the marketplace.

In 1986, massive amounts of brown diamonds were brought to the market. Rio Tinto opened the Argyle mine in Australia, which 80% of the diamonds mined were brown in color. DeBeers followed this trend and in 1996 introduce massive number of brown diamonds to the market. These brown diamonds were previously only used for industrial purposes.

The value of brown diamonds was hard to determine since the GIA 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 represents the darkest hue.

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,' in 2014 the number jumped to 400,000 times a year.

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

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