The art of the diamond cutter

Press, 1 September 1980, Page 26

The art of the diamond cutter

The aim of the diamond cutter is to make the most of the diamond’s high reflectivity and refractivity. ' The cutter too has often to make the most of an imperfect rough stone given to him for faceting. , In his “The Art of the Diamond Cutter,” A. Monnickendam wrote: “The master cutter is constantly on the alert for ways of eliminating, marks and imperfections of aIT kinds, and at the same time aims at the best possible weight consistent with correct proportions.”* .. . It will be appreciated from this that the diamond cutter has first of all to study his stone. This is usually the job of the designer, who is often the head of the firm. After he has studied the stone, he will mark it with Indian ink as a guide to the men who will do the actual work on it.

Suppose that the rough diamond to be cut is an octahedral crystal, the classic shape, and not one of the irregularly shaped stones that make up a considerable proportion of all the. diamonds recovered.

The technique of shaping a rough diamond is by splitting it along one of the cleavage planes with a steel blade, but the removal of the point of an octahedral crystal is more usually done by sawing than by cleaving. In a diamond-cutting factory there are batteries of saws, and the operative in charge of these, mounts the rough stone in cement and fits it between two holders.

The stone is then held, by the pressure of a counterweight, against the edge of the saw. The saw, consisting of a paper-thin disc of bronze impregnated with a paste made from powdered diamond, rotates at 6000 revolutions a minute.

Surely, but very slowly, diamond cuts diamond. It takes five eight-hour days to saw through a ten-carat stone.

The next operation is to round off the stone to create the girdle dividing the top,, or the table as it is called, from the base, or pavilion. This rounding operation is known as “bruting,” and is done by rubbing one diamond against another. One stone is held in a lathe and the other is cemented into a handle so it can be held against the stone in the lathe with the necessary force. Once the stone has been rounded the faceting begins. This is done on a turntable called a “lap,” which is impregnated with a mixture of diamond dust and olive oil. The diamond

is held in a “dop,” a small metal cup with adjustable claws. In the first faceting operations, which are carried out by the “cross-worker,” the flat table is polished on the top of the stone, and four facets are polished above, and four below, the girdle. The angles of these, and indeed, those of all the facets, are critical. Unless they are correct they will not fully reflect the light falling on them through the table, and the stone will lack brilliance.

Next, the stone passes to the brillianteer (or brilliandeer, or finisher). He puts on the other 48 facets to make up the total of 57. When the brillianteer has finished, the sides of the stone will be broken up into a pattern of stars and kites.

Apart from the round brilliant-cut, there are oval brilliant-cut stones, pearshaped brilliant-cut stones, sometimes called drops or pendaloques, and there are the nowadays' very fash-, ionable boat-shaped or marquise-shaped brilliantcut stones. The cutting of these fancy shapes calls for more skill and knowledge than the cutting of round brilli-ant-cuts, and this is reflected in the relatively high price asked for them. The cutting of emeraldcuts, sometimes called

.square-cuts or trap-cuts, is also very exacting. An emerald-cut stone has 16 traps above and 24 below the girdle. A diamond much used in modern jewellery is the long rectangular baguette. This is a simplified stepcut. From time to time the jeweller will also come across diamonds in other styles. In older pieces he will find many rose-cut stones, having flat bases, and a pointed top in which 24 triangular facets have been cut. This is an old

Indian style of cutting which was introduced into Europe during the seventeenth century, being very popular until it was superseded by the modern brilli-ant-cut. Then, too, there are sim- I plified versions of the brilliant-cut which are used for small stones. Among these is the eightcut which, as its name suggests, has eight facets on the table and a further eight on the pavilion. Diamonds have been cut in many other and sometimes very complicated ways, such as the Jubileecutin celebration of Queen Victoria’s Jubilee. But stones cut in this way are seldom met with. Perhaps, however, a recent experiment in diamond cutting should be mentioned. In 1961, A. Nagy intro-

duced the profile-cut. Nagy had taken thin slices of diamond, and had cut ridges on them at rightangles to one another so that the stones looked rather like miniature reflectors, similar to those used on bicycles. After some initial interest in this cut, which was very economical of material, the trade has shown little enthusiasm for it.