Hello Phillip
Since we are in a bit of a news funk and some unrelated subjects are creeping in to the thread, I thought this might be of interest to those who may not be as completely up on what its all about as some others might be.
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A few days ago in history: January 26, 1905
The superintendent of the Premier Diamond Mine in South Africa was making a routine inspection when he discovered the largest diamond ever found. The 3,106 carat (1.37 pounds or 621.2 grams) monster was named the Cullinan Diamond, after the developer of the mine, Sir Thomas Cullinan.
The Cullinan Diamond was cut into more than 100 finished gems: Contrary to what you may have believed, diamonds do not come glistening brilliantly from the earth. In their raw form, in fact, they are rather dull-looking lumps of carbon. What turns these undistinguished stones into the sparkling gems we admire so much is the highly skilled, equally arcane process known as cutting.
Origins of Diamond Cutting:
Cutting raw diamonds to enhance their brilliance (and thus their value) is a very old profession. There are reports of a diamond cutting industry in Renaissance Venice as early as 1300, and the profession is thought to have been practiced in Paris (then the most important market for diamonds) not long afterwards. Another early cutting center was located at Bruges, Flanders; and nearby Antwerp and Amsterdam soon developed their industries as well. What all these early diamond cutting centers had in common was access to the trade routes by which the raw stones were moved from the mines of India (and in the eighteenth century, those of Brazil) to Europe.
These early cutters were most concerned with keeping as much as possible of the original weight and shape of the gem, and less with enhancing its brilliance. Therefore, gems cut before the mid-seventeenth century were generally cut flatter than is the case today, when brilliance is the most valuable quality. As the number of diamonds reaching the European market began to increase, cutters gained in skill and knowledge, and began to employ new patterns. Where sixteenth century gems generally had no more than 24 facets on the top of the stone, by 1700 that number had risen to 58. Still, stones cut in this period lost light through the sides and bottom: maximum refraction was not to be achieved until the current century. Modern Diamond Cutting Credit for creating the modern "brilliant" cut goes to Marcel Tolkowski, who in 1919--when he was just 21 years old--published a book called Diamond Design. In this work he calculated theoretically the precise angles and proportions which would give the best optical results--combining reflection and refraction to produce gems which give the maximum "fire" or refraction while retaining a high degree of reflection. The modern brilliant cut diamond is shallower than the 1700 "mine cut" stone, and departs further from the natural angles found in raw diamonds. Secondly, the girdle--the axis marking the widest part of the finished stone, and the place where the top of the stone meets the underside--is round. Brilliant cut stones sacrifice something like half the raw carat weight to achieve this maximum compromise between reflection and refraction, but their flashing brilliance makes up in value for the loss of raw bulk.
The diamond-cutting process also exemplifies Man's disgust of waste: During the course of the cutting of a typical diamond there is sometimes as much as a 50-60% "loss" of material, the dust of which eventually gets recycled for use in a paste that coats skeifs, automated saw blades and other diamond-cutting implements.
There are usually five steps in the diamond-cutting process: inspection, cleaving, sawing, girdling, and grinding and polishing (regarding the last two of the aforementioned as one step).
Inspection.
The first step in the cutting of a diamond is inspection. As the octahedron is the most common crystalline structure of diamond, every effort is made on the part of the diamond cutter to be able to recognize the octahedral faces embedded in the rough diamond. Another thing for the diamond-cutter to keep in mind is the inclusions (the imperfections of the raw diamond), which must be kept to a minimum in the finished diamond. This preliminary stage can sometimes, for large diamonds, take many weeks.
Cleaving.
The next step in the diamond-cutting process is cleaving. Despite the advances of modern technology, the most efficient way of actually cleaving a diamond is still by hand. Contrary to popular conception, diamonds are not indestructible and, in fact, are very vulnerable along the cleavage planes (the octahedral planes along which the diamond will be cut). So this is a very crucial step indeed.
Either a laser beam or another diamond is sometimes used to make the initial ink-marked notch along the grain. After this notch (called a kerf) is made, a knife blade is placed within it and is struck with a wooden mallet or an iron rod. The skill and experience of the diamond cutter and the extent to which he made his preliminary inspection will determine how clean a cut he made. He repeats this process along all cleavage planes until he has, more or less, an octahedron.
Sawing.
The next step in the process of diamond-cutting is sawing--that is, cutting the octahedral diamond slightly above the central square plane of symmetry, yielding an inchoate form of the brilliant cut diamond and a pyramid which can then be used to make another brilliant cut diamond. If the diamond-cutter decides, however, that for some reason the octahedron is not fit to be turned directly into a brilliant cut diamond, then he can split it exactly along the plane of symmetry, yielding two pyramids which can then be turned into brilliant cut diamonds. Using such a blade, it typically takes a full working day to divide a one carat stone.
Girdling.
The next step in the process of diamond-cutting is girdling--rounding out the sharp edges along what used to be the square plane of symmetry, forming the circular girdle. This process was previously achieved through bruting, a process which entails cementing the diamond into a wooden stick and rubbing it fiercely against another diamond cemented in a stick so as to round the sharp edges.
Currently, the girdling is achieved by cementing the diamond to be cut in a holder (dop) that is then screwed to the chuck of a motor-driven lathe. While the stone is spinning in the lathe, a second diamond is carefully rubbed up against it to create the roundness. The result of this process is a clearly defined girdle, pavilion (the conical base), and crown (the flat-topped upper portion).
Grinding and Polishing.
The final step in the process of diamond-cutting is grinding and polishing. It is during this step that the actual facets are formed, smoothed and polished. The brilliant cut has 58 facets, the first 18 of which--the fundamental facets--are fashioned symmetrically and precisely using a skeif, which is a circular rotating disk charged with crushed diamond and olive oil.
Diamond Cutters
Cutting is a long and exacting process, and an experienced cutter may work by eye alone.
Famous Diamond Cuts
One indication of just how important the skilled diamond cutter is to the industry comes from the story of the Cullinan Diamond, at 5,106 carats the biggest rough diamond yet discovered. It was cut by Joseph Asscher of Amsterdam for King Edward VII of Great Britain.
Asscher studied the rough stone for two full months before deciding how it should be cleaved. At last, in February, 1908, he made a groove in the rough diamond and struck it with an iron rod. On the first stroke, nothing happened; but on the second attempt the diamond divided exactly as Asscher had planned. He went on to produce from the original stone the largest cut gem in the world, the Star of Africa, which today is in the head of the Royal Sceptre and is on exhibit with the other crown jewels at the Tower of London. The Cullinan also produced eight other major gems, all of them in possession of the British government or the royal family. As his pay for the tremendous job of cutting the biggest diamond in the world, Asscher was allowed to keep all the smaller pieces of the Cullinan--very worthwhile remuneration indeed.
Cutting to the Bottom Line It is said that there are four qualities that determine the value of a cut diamond--clarity, color, carat weight and cut. Of these, none is more important or more in control of human agencies than cut. The skill and experience of the cutter can make all the difference in the ultimate value of a raw diamond.
Hope it was interesting.
Regards |
