A Step-By-Step Look at How a Colored Diamond is Cut.

Nature gives us the wonder of a diamond, but it is the cutter’s skill that turns that gem into an object of beauty and desire. One part mathematical calculation, one part art and one part experience, the diamond cutter’s talent brings out the best in a rough stone.

The best, however, varies dramatically from diamond to diamond. When cutting a white diamond, the goal is to bring out the clarity, make it colorless and give it the greatest sparkle with the most weight retention.

The rules change when cutting a fancy color diamond, where the value of the stone lies predominantly in the saturation of its color. In this case, the cutter works to enhance the color in the best way possible. While every effort is made to retain weight — as it is still a major component in the value of the stone — in some cases, weight might be sacrificed to coax maximum color out of the diamond.

Rapaport Diamond Report followed the polishing process of a 4.23-carat rough octahedral yellow diamond from New York–based Scarselli Diamonds, a firm that specializes in fancy color diamonds. Scarselli Diamonds purchased the rough at an auction in South Africa during 2009.

Getting Started

Before actually cutting the rough, it is examined carefully, evaluated from all perspectives and analyzed in detail to determine how best to maximize the beauty and size of the stone that will result in maximum profitability. Decisions throughout the cutting process are based on a combination of many factors. Some are objective — magnified views and technical measurements of the stone. Others are subjective — the opinion of the cutter, based on his professional instincts and career of experience cutting other stones.

As part of the examination of this particular rough, a Sarin machine is used to generate illustrations that act as patterns of the possible shapes and weights of the stones that could be produced. These illustrations allow Scarselli Diamonds to see the full range of options for cutting the rough and to calculate and compare — based on shape, weight and number of cut diamonds — the value of the stones that could be produced from this particular piece of rough.

After considering all the various shapes and weights that could potentially be produced, Scarselli Diamonds chooses to create a single 2.50-carat emerald cut, valued in the price range of $100,000 to $112,500 wholesale.* Another possibility would be to cut the diamond as a radiant, bringing out more of the orange tones, but Scarselli Diamonds principals feel that a predominantly yellow color will be more marketable.

The shape of any final polished diamond is determined, in large part, by the shape of the rough from which it is cut. Some rough is formed in such a way that it determines the shape of the diamond. Other rough can accommodate a number of different shapes and, depending on the size, perhaps even a number of individual stones. Since the Scarselli Diamonds rough is an octahedron, it has the potential to be cut into a variety of shapes.

The color of the rough is a vibrant, highly saturated yellow with orange overtones. It was hoped that the final polished diamond would earn the color descriptor of Fancy Vivid from the Gemological Institute of America (GIA) when graded — which it did. After the stone was cut, the GIA graded it as Fancy Vivid orangey yellow, VS1. The final weight was 3.07 carats. Pricing of a polished color diamond is greatly affected by the saturation of color in the diamond and the fancy color grade that it receives.

There are two ways to start the cutting process. The first is to saw off the top of the stone in one fell swoop and cut a second, smaller diamond from it. But this approach does not allow for periodic pauses in the cutting process to re-examine the stone at various stages and from various perspectives. Also, in this approach, the tip of this stone that would be cut away would be approximately 0.16 carats. That would yield a polished stone of only about 0.08 carats. It is decided that is too small a stone and of too little value to give up the control of monitoring the cutting of the stone more closely.

To start the cutting process, the tip of the rough is cut away, layer by layer, on the polishing wheel. The first step in the faceting process is the table facet, which allows for a closer look at the internal structure of the diamond. When the diamond is examined again, at this point, it is revealed that there are two clouds and one small crystal present, indicating that the stone is probably a VS1 clarity. It also is noted that the inclusions are deep in the stone and pose no threat to the cutting process. They also are too deep to be cut out.

The cutter’s magic

As the diamond cutter performs his wizardry — and makes his ongoing assessments — changes evolve in the plan for the diamond. As the cutter starts working on the rough, his analysis of the diamond leads him to believe that he will be able to retain more weight. In fact, he feels that he can fashion the rough so that the finished diamond will be more than 3 carats instead of the 2.50 carats the Sarin analysis suggested.

As the stone is being faceted, some naturals are revealed on the girdle. A decision has to be made as to whether or not to remove the naturals or open the table more to perfect the color. It is determined that the naturals do not interfere with the beauty of the stone, so the decision is made to further open the table.

In order to maximize the weight, the cutter advises keeping pointed corners, instead of cutting faceted corners, on the girdle. While the pointed corners do enhance weight, they also are known to diminish light. But it is the light that brings out the color in a stone. However, the color of this rough is already so strong that the cutter does not consider diminishing light a problem. The additional weight raises the value of the stone to an approximate price of $135,000 to $150,000. In the end, the cutter was able to maintain a 73 percent weight retention for a 3.07-carat finished diamond.

The transformation from rough to polished is a unique journey for each and every stone and one that needs to be carefully and continuously monitored in order to bring out the inherent natural beauty of the diamond. The stone reveals important characteristics about itself during each step of the cutting process. It is important for those working with the stone to be open to those revelations because it will allow them to take advantage of the diamond’s unique qualities to produce a more beautiful diamond that sings its magic song.

Article from the Rapaport Magazine - February 2010. To subscribe click here.