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 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 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
Baumgold Bros., a 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 had 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, in which 80% of the diamonds mined were brown in color. DeBeers 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 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
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 not even 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.