Once mined, diamonds must be sorted before they can be cut or polished. While the world’s largest and advanced sorting facility is located in Botswana, many countries and companies are beginning to keep their diamond sorting in-house. Initially, diamonds are divided into gem quality diamonds (highest quality, used for jewelry), industrial diamonds (mid-quality, used in industry, often for cutting other diamonds), and crushing-boart or boart diamonds (lowest quality, crushed and used in polishing process) (Rough Diamond Sorting, 2015).

Once gem quality diamonds are isolated, they are further sorted based on their carat, cut, clarity, and color. 


Diamonds, like gold, are distinguished by “carat,” or mass. One carat equals roughly 0.2 grams. Carat factors greatly into the worth of the final product, with comparable stones of a higher carat often being more desirable than stones of a lesser carat. Rough diamonds will generally fall into one of four categories based on carat: “Smalls,” weighing .65 carats or less; “Grainers,” weighing between .66 and 1.79 carats; “Large Stones,” weighing 1.8-10.79 carats; and “Special Stones,” weighing anything more than 10.8 carats (Sorting and Valuing, 2013).

rough diamond

Most engagement ring diamonds fall into the “large stone” category, while perhaps the most famous “special stone,” the Hope Diamond, weighed just over 112 carats uncut (Department of Mineral Sciences, 2003).

Cut (shape/model)

Because diamonds form in a cubic system, rough diamonds can be found in any number of shapes. Primarily, though, rough diamonds tend to be octahedral (eight-sided), dodecahedral (twelve-sided), cubic (six-sided), or rhombododecahedral (twelve-sided with rhombic faces) (Rough Diamond Sorting, 2015).


Diamonds are then divided into “sawable,” “makeable,” or “cleavage” diamonds (Caspi, 1997). “Sawable” diamonds, often octahedral or dodecahedral, will be sawed to create two stones when polished. “Makeable” diamonds are often already broken octhedrons or dodecahedrons. They will only create one stone when polished, and usually require more work during the cutting and polishing process (Caspi, 1997). The least common, “cleavage” diamonds are irregularly shaped diamonds that require special attention and unique approaches during the cutting and polishing process. The cut of the rough diamond has the largest impact on how the stone will eventually be cut.


The clarity, or measure of impurities within the diamond, has perhaps the greatest impact on the diamond’s ultimate worth. Based on the size, number, placement, and type of impurities, clarity will factor greatly into the final cut of the diamond. A diamond without any cracks, impurities, or inclusions is extremely rare and thus is far more valuable than a diamond of similar shape and size. Many sorters refer to the Gemological Institute of America (GIA) clarity scale, which ranges from “flawless” diamonds, which exhibit no blemishes, to “included” diamonds, which contain obvious blemishes that may affect transparency and brilliance (Gemological Institute of America, 2015).




Finally, diamonds are sorted by color. While the stereotypical diamond is both colorless and clear, diamonds come in a variety of colors and shades. The clearer and more colorless a diamond, the more the diamond is worth. Most diamonds are sorted using the GIA D-Z color scale, on which D is colorless and Z has the highest presence of color (Gemological Institute of America, 2015).


Naturally colored diamonds, or diamonds exhibiting color other than brown or yellow, are considered “fancy” diamonds and are not rated based on the GIA color scale.



While sorting is a vital part of the commodity chain, most sorting is done either at the mining facility or the cutting and polishing facility, so oftentimes any environmental or social impacts related with sorting have more to do with either the mining or the cutting aspect. The diamond trade as an industry, however, particularly the Diamond Trading Company in Botswana which is the largest diamond sorting facility in the world, has brought millions in revenue and thousands of jobs into an economically depressed region of the world (Sorting and Valuing, 2015).

Although public opinion of the southern African diamond industry is often shadowed by reports on illegal trading, blood diamonds, and dangerous working conditions, the industry is not so bad as it might seem. In Botswana in particular, the diamond trade is the second largest industry and is either directly or indirectly responsible for over 4,000 miles of road and a country-wide digital telephone line, as well as vastly improved public services (Bertoni, n.d.). Because of the increase in revenue within the country, other industries are beginning to rise up, further bolstering the economy. And as Botswana and other third world countries become more globally integrated, there is a trend of improving business practices, justice systems, and working conditions, not to mention an increase in quality of public services such as health care, education, and public transportation. Countries historically dominated by primary economic activity, or resource extraction, are beginning to now integrate the next steps into their industries (i.e. Botswana not only mining but now sorting and trading their diamonds), they are able to move to the more stable and more lucrative secondary and tertiary economic activities, which include industry-and-service-based economies. In this way, underdeveloped countries are gradually bringing themselves up to pace with the rest of the industrialized world and may some day have hope of competing on a global scale, as well as improving their citizens’ standard of living.


One thought on “Sorting

  1. Thank you; can you please tell me what is the difference (in carat weight) between – 9 and +9 diamond screen sizes?

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