Diamonds – From Rough to Polished
By Devorah Isenberg , Thursday, March 03, 2011
A diamond is just a sparkling little colorless rock that looks pretty in an engagement ring, or set into a pendant or pair of earrings. So why is it the center of every engagement, the symbol for all things valuable and precious, and the proverbial girl’s best friend? How is a rough diamond made into a sparkling gem? Why do we buy diamonds anyway?
The difference between a piece of rough diamond and a finished jewel is a time-consuming process of cutting and polishing. The secrets of diamond cutting have been honed over generations, passed down in the small circles of knowledgeable diamond experts. When you buy a certified loose diamond, you hold a piece of that secret knowledge and expert craftsmanship in your hand.
A rough diamond crystal has none of the sparkle and brilliance of a cut diamond
Cutting diamonds is unlike cutting any other gem because of the unique hardness and value of the diamond. Diamond cutting requires special knowledge, tools and techniques, and is done in only a few cities worldwide. Antwerp, Belgium is one major diamond cutting center, as well as Surat, India. Cut diamonds are also manufactured in New York City and Tel Aviv, Israel. When you buy diamonds, you are purchasing a piece of that globe-circling tradition.
The first step of diamond cutting is planning. The diamond cutter analyzes the rough diamond with computer imaging technology and with his own highly trained eyes to determine how the loose diamond will be cut. He tries to plan a diamond shape that will maximize the size of the finished stone and minimize waste, as well as a popular shape that will sell quickly. Any inclusions or imperfections are notes and incorporated into the 3-D computer model, so the cutter can cut the stone in a way that excises or hides the imperfections
Computer imaging helps the cutter plan the ideal cut for each crystal
Nothing replaces the painstaking process of examining each stone by hand
During the planning process, the cutter evaluates the yield and weight retention of the diamond. His goal is to extract maximum value from each piece of rough. This means that he looks for the best way to create a finished gem on the basis of its per carat value. For example, by one plan a 2.00 carat rough diamond may produce two gems of .50ct each when finished. Planning differently might yield diamonds of .70ct and 30ct. If the value of the latter combination is more than the former, then that is what his plan will be. Clarity characteristics or inclusions in the rough stone will also factor in to the plan as certain approaches might exclude some flaws thereby increasing the value of the finished diamond.
The natural shape of the diamond crystal will also impact what shape diamond is cut. Octahedron crystals are usually cut in round or square brilliant cuts, while odd shaped crystals such as macles will often be cut into fancy shapes like emerald or radiant.
Despite the cutter’s skill and precision and the advanced technology used, the cutting of a diamond always results in the loss of about half the weight of the original rough diamond. The planning stage of diamond cutting always involves critical decisions balancing cut quality against carat weight. Certain carat weights are considered special such as 1.00, 1.50 and 2.00. You will often see liberties taken with cut quality of stones right at these “magic marks”. To perfect the cut often means dropping below them and therefore losing some per carat value. This is because diamond per carat value is a geometric progression as the diamond gets bigger in size and rarer in nature. For example, where a 1.00 ct diamond is worth X , a 2.00 ct diamond may be work 3X. So the price per carat increases for the same quality as the diamond increases in size, compounding the total value of larger diamonds.
The next stage of diamond cutting is cleaving or sawing. This involves the use of a diamond-edged saw or laser to carefully cut the diamond into the specified pieces. Because of the diamond’s natural hardness, the saw must be edged with actual diamonds in order to cut through the rough stone.
The diamond then undergoes the process of bruting. Two diamonds are set on spinning axles and made to grind against each other, to shape each diamond into its destined round shape. Next is the crucial step of brillianteering—the delicate and all-important placement and cutting of the facets. This step is one of the most important in determining the light performance and brilliance of the finished diamond. Finally, the diamond is polished—facets are cut into the stone and the cut surfaces are polished to a mirror finish.
Of course, after the diamond is cut and polished, it is thoroughly inspected. The loose diamond is cleaned in acids to ensure that not a speck of dust remains, and then it is examined to see if it meets the quality standards of the manufacturer. Not all manufacturing facilities are alike—some hold each diamond to the highest standards of excellence, while others focus on mass-producing diamonds cheaply.
Cut diamonds are sorted before being packaged and sent to wholesale markets
Once inspected, the diamond is sent to grading facilities and labs to be officially weighed and measure as well as graded for color, clarity, cut and cut quality. Each certified diamond is given a unique report number. Some retailers buy diamonds for their own inventory while others are brokers who sell diamonds that are loaned to them on consignment.
Finally, the diamond arrives into your hand, either loose or possibly set into a brilliant engagement ring. The many facets act as tiny mirrors creating a sparkling display of light. The end result is a mesmerizing tribute to ancient knowledge and modern technology, and an eternal symbol of love and devotion.
A truly well-cut diamond has un-matched brilliance and fire
For more specific questions ask our experts