Diamonds That Are A Cut Above

The Economist Technology Quarterly writes:
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Materials Science: The combination of an expert systems and a novel laser cutting technique could boost the value of rough diamonds.

While a diamond may be forever, its value is far from set in stone. It depends on the four C’s: carat, cut, color and clarity. But while the first three can be measured objectively, assessing a diamond’s clarity involves a certain amount of subjectivity and can leave experts disagreeing about the grade—and hence the value—of a stone. Now researchers at Cambridge University’s Institute for Manufacturing claim to have devised a way to make the grading of diamonds and other precious stones more consistent. Tony Holden, the project’s leader, says automating this process could do more than just lead to more accurate valuations. It could also make rough stones more valuable, by reducing the amount of waste during cutting.

Even a small improvement can yield a significant increase in value, says Dr Holden, who specializes in applying technology to improve decision making in business. Together with his colleague Matee Serearuno, he has developed an optimization system called iGem. Besides automatically working out the grade of a rough diamond, it also suggests how best to cut it in order to maximize the value of the resulting stones.

The system uses a set of rules, distilled from the judgments of four diamond experts, to determine the clarity, and hence the grade, of each stone. Each expert was asked to classify 503 different ‘virtual stones’—computer models of stones containing different types of flaws. The expert’s verdicts were then boiled down into a set of rules, so that when a new gemstone is presented to the system, it can determine how the experts would probably have graded it. Data from more experts could have been used, but four proved to be enough to product a robust and accurate system, says Dr Holden.

In actual use, the system is fed models of gemstones, which are produced by scanning the stones using a desktop x-ray tomography machine. When a stone is identified as a borderline case between two grades, the system uses an optimization technique, called genetic algorithm, to explore the different ways in which the stone could be cut to maximize its value. Sometimes bigger is not necessarily better: removing imperfections, known as inclusions, may reduce the size and caratage of a stone, but could increase the value of a rough stone by as much as 23%.

For over 600 years lapidarists, or stonecutters, have been using essentially the same techniques to cut diamonds and determine their value, says Dr Holden. There is a great need for automation, he says—a sentiment echoed within the industry. The Gemological Institute of America, for example, is devising software to enable retailers and consumers to compare diamonds of different cuts by grading the cut automatically.

The next logical step is to automate the physical process of cutting the diamond, and Dr Holden seems to have found the ideal partner. He is talking to Calibrated Diamonds, a company based in Johannesburg, South Africa, about combining his optimization techniques with an advanced laser-cutting system. Traditionally diamonds are cut and polished using other diamonds. But in recent years, lasers have been introduced to make rough cuts and to carry out bruting, the beveling process used to give diamonds their characteristic sharp-edged shapes. John Bond, the founder of Calibrated Diamonds, says his laser cutting method can make much more precise cuts and can even polish diamonds, though he is reluctant to explain how it works. He believes that combining his laser cutting with Dr Holden’s software, and automating the whole process, could both reduce waste dramatically and cut the turnaround time from months to days. “Currently, people are losing up to 70% of the diamond,” he says.

Mr Bond hopes that this combination of technologies will help his home continent to benefit more from its natural wealth. More than 60% of the world’s rough diamonds come from Africa, he says, but a lack of expertise and relatively high labor costs means that the stones are usually shipped overseas, to countries such as India, for assessment and cutting. He hopes to have his first factory up and running later this year.