Also known as chocolate, champagne or cognac diamonds
Author: Hobart M. King, Ph.D., GIA Graduate Gemologist
What Are Brown Diamonds?
Although most people think of diamonds as colorless gems, most natural diamonds are a faint to dark brown. For nearly 100 years, De Beers, the company that controlled the diamond industry, did not want brown diamonds in the gem diamond market. They ordered all brown diamonds that they mined or acquired to be crushed for use as abrasive granules. Because of this brown diamonds had very little value.
Then, in the 1980s, owners of the Argyle Mine in Australia had a lot of brown diamonds and a very bold idea. Instead of selling their brown diamonds to De Beers for a pitance, they shipped millions of them to India, where low-cost workers cut them into melee-size gems - many as small as one point in weight.
The tiny brown stones then entered the market in popular-priced jewelry. A dozen or so of these tiny brown gems brought an exciting scintillating to a piece of jewelry. A hundred of them in a pavé setting produced a spectacular result. The attractive appearance and low cost of the jewlery was a great success and it attracted a new group of buyers to the diamond jewelry market.
Very few people noticed the brown color because the gems were so small and the scintillation so spectacular.
Today, brown diamonds are sold under trade names such as "chocolate diamonds," "champagne diamonds," and "cognac diamonds." Clever marketing, fresh designs, and low prices converted brown diamonds into a profitable product and a new jewelry category.
The Origin of Brown Color
Many brown diamonds are thought to derive their brown color from being subjected to stress during their history in the Earth. This stress deforms the diamond crystal lattice which produces a texture known as "graining" within the diamond crystal. This graining is sometimes visible during microscopic examination as a series of parallel to subparallel grain lines similar to the "grain" seen in a piece of wood.
The deformed crystal lattice changes the way that light passes through the diamond. It causes the diamond crystal to absorb many wavelengths of light and visible light that reaches a human eye causes us to see the diamond as "brown".
Brown graining is typical of brown diamonds from the Argyle mine in Australia. Some of the pink diamonds from Argyle likely receive their pink color from similar graining.
A Bit of Diamond History
In the late 1800s and early 1900s, enormous diamond discoveries in South Africa created a problem. So many diamonds were suddenly available that their free entry into the market would depress prices. De Beers gained nearly complete control of the global diamond supply and released diamonds into the market at a rate that maintained prices.
De Beers then stimulated demand through their "A Diamond Is Forever" marketing campaign. Many advertising experts believe that De Beers ran "the most successful ad campaign in the history of marketing." Growing demand and a tight control over supply made a lot of money for De Beers.
At that time - and continuing today - many people believe that the standard of diamond beauty and value is a clear, colorless stone. De Beers considered brown diamonds unsuitable for jewelry - but was that really true?
Brown Diamonds from Argyle
In the mid-1980s the Argyle Mine in the East Kimberly region of Western Australia began producing diamonds. It quickly became the largest diamond producer in the world on the basis of carat weight.
The Argyle Mine produced a small number of clear, colorless diamonds and a small number of vivid fancy diamonds in pink, red, and blue colors. But, most of the rough coming out of their mine did not meet De Beers definition of "gem quality."
About 80% of the Argyle rough was brown, under 0.1 carat in size, and most stones had clarity problems. De Beers, the company who held a near monopoly on diamond rough at that time, was only willing to pay an industrial-grade price for these diamonds.
Managers at Argyle stopped selling their diamonds to De Beers. They decided to sell their colorless diamonds and fancy-colored diamonds themselves. And, they sent their brown rough to India where skilled but low-cost workers cut it into tiny round brilliant diamonds. Many of these tiny gems were as small as 0.01 or 0.02 carats.
The brown color of the rough was less obvious in gems of this size, and dozens of them could be set in a single piece of jewelry. The jewelry was inexpensive but hundreds of light-reflecting facets in each piece produced a wonderful scintillation that many people enjoyed. Argyle turned a rejected product into a new and profitable niche in the diamond jewelry market. 
Champagne and Cognac Diamonds?
The brown-colored diamonds from the Argyle mine were given interesting names. These names were inspired by modifying hues of yellow or red that accent the appearance of the brown diamond. Light yellow-brown to golden-brown stones were called "champagne diamonds." Darker orange-brown and reddish-brown stones were called "cognac diamonds".
Fresh, attractive, scintillating, and inexpensive, the Argyle diamond jewelry immediately appealed to many customers. Brown can be beautiful and people purchased these stones because they liked them!
When life gives you lemons, make lemonade. When a mine gives you brown diamonds, you can make your choice of champagne, cognac, or chocolate. :-)
What Are Chocolate Diamonds?
In 2000, Le Vian, a jewelry design and manufacturing company, began acquiring Argyle diamonds in a limited range of brown colors. They called these gems "Chocolate Diamonds ®" and trademarked the name. Many of their "chocolate diamonds" were set in jewelry made from "Strawberry Gold ®" - a Le Vian gold alloy with a reddish color. Thirty years earlier these "Chocolate Diamonds ®" would have been made into cutting abrasives. Now, they had become a diamond jewelry trademark.
Cocoa, Coffee, Amber, Caramel, and Khaki Diamonds
Brown diamonds, because of their abundance, were probably the first diamonds to be used by people as gems. Jewelry set with brown diamonds has been found among the artifacts of ancient Rome and India. Today, people call them a variety of creative names that include "cocoa diamonds," "coffee diamonds," "amber diamonds," and "khaki diamonds." Other interesting names will likely be invented in the future.
Color Grades for Brown Diamonds
Brown diamonds are recognized in the famous D to Z diamond color grading scale developed by the Gemological Institute of America. Diamonds graded K to M with a distinct brown color are given a letter grade and termed “faint brown”. Those graded N to R receive a letter grade and the term “very light brown” and those graded S to Z receive a letter grade and the term “light brown".
Brown diamonds on the D to Z scale will generally sell for prices that are less than similarly-graded diamonds without the brown color. In addition, the color was graded with the diamond positioned in the table down position - so the color grade is a body color rather than the face-up impression of the color.
Beyond the D to Z scale, diamonds with a distinct brown color might earn a grade of Fancy Light, Fancy, Fancy Intense, Fancy Dark, Fancy Deep, or Fancy Vivid, depending upon their appearance determined by the combined effect of hue, tone, and saturation. All of these Fancy color grades are determined by examining the gem in the face-up position. That makes the color assessment more similar to what a buyer will experience if the diamond is displayed or used in jewelry.
Uses of Brown Diamonds
Brown diamonds have uses beyond those in the contemporary women's jewelry described above. The history of brown diamonds being used as a gem goes back for nearly 2000 years, perhaps longer. Rings set with brown diamond crystals were being made by Roman artists between the first and third centuries C.E.  At that time methods for cutting and polishing diamonds had not been developed, but setting a natural crystal in a ring was a good alternative.
For the company's first 100 years, De Beers considered brown diamonds to be unsuitable for use in jewelry. Brown diamonds mined by the company or purchased from other producers were sent for industrial use. Many of them were crushed and used to make industrial abrasive granules. The granules were used to line the cutting surfaces on diamond drill bits, grinding wheels, abrasive papers, saw blades and other tools.
Some of the larger brown diamonds, free of fractures and inclusions that would lower their durability, were used to manufacture specialty bearings or wear-resistant parts. Others were fashioned into dies used to manufacture wire. 
Today, brown diamonds from Argyle and other mines are appreciated around the world, especially in the United States fashion jewelry market. They are also gaining popularity among rising middle class consumers in China and India.
Brown Diamonds for Men!
Brown diamonds have become especially popular in men's rings, cuff links, earrings, watches, and other jewelry. Brown is a masculine color. Brown diamonds are attractive and cost less than colorless diamonds of the same size and clarity. Brown diamonds make great sense for men in many ways.
 Diamonds Are for Everyone: Article on the Rio Tinto website, accessed March 2018.|
 The Nature of Diamonds by George E. Harlow, Cambridge University Press, 1997, 288 pages, ISBN-10 0521629357.
Brown Diamond Treatments
Brown diamonds are sometimes treated, but these treatments are usually done to convert them into diamonds of other colors. Brown diamonds owe their brown color to lattice imperfections thought to be a result of geologic forces applied to the diamonds at some time during their long history. High-temperature, high-pressure treatments have been used to convert many brown diamonds into attractive yellow or colorless diamonds. These diamonds are more valuable than brown but less valuable than natural, untreated diamonds of similar color and quality.
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