Diamond Cutting: Splitting, Cutting, and Polishing

The process of diamond cutting, which includes splitting (or cleaving), cutting, and polishing (which includes setting and polishing the diamond)

The cutting of the diamond includes three series' of operations: the splitting or cleaving; the cutting, properly so called; and the polishing. Special workmen are required for each one of these branches. (The illustrations in this section relating to diamond-cutting are taken from fine water-colour drawings sent from Amsterdam and executed specially for this work.)


It is to the splitter that the rough diamond is given; his quick penetration and ready action are to determine the future of the stone.

First of all, he examines very carefully the little morsel in his hand; he decides how it should be shaped to retain the utmost weight with the most brilliant effect; he detects every flaw and streak, and he knows whether the imperfections are at the stone's surface or at its heart. Very quickly then he sets to work. He takes a longish wooden implement or baton, shaped so as to be conveniently held in the hand, and having at one end a ferule extending a little beyond the wood and filled with a mastic or cement of resin and brick-dust. This cement he softens by heating it at a lamp, then embeds the diamond in it and lets the cement cool, by which means the diamond is firmly fixed in its place. With another diamond, sharply edged and secured in the same way, he cuts a notch in the diamond he is about to split. This notch is of a V shape, and must lie exactly in the direction of the cleavage-plane of the stone-a result which, though apparently so difficult, is easily attained by the practised eye and dexterous hand of the workman. A box beneath his work catches the dust, and a little sieve sifts at once the diamond-powder from the particles of resin dropped.

When the notch is cut deep enough the workman places the wooden baton upright in a hole in a block of lead before him; then introducing with one hand the blunt edge of a small steel ruler into the notch of the diamond, with the other he strikes the ruler a smart blow with a steel rod, and the stone is split. It is not without emotion that one sees this blow given, for the slightest error may prove fatal to the diamond's value for ever; but it is given without hesitation and with perfect composure.

The stone, which is now divided into two parts, is removed from the cement; the main part undergoes a repetition of the operation until it has received its proper form and all flaws are removed; and the fragments are carefully preserved to be cut into little roses, which, however small, have a value.

In Fig. 112 a general view is given of the room in which the splitters work in Coster's establishment at Amsterdam. Fig. 113 shows on a larger scale the complete arrangement of every division in this vast workroom.

Fig. 115 is an illustration of the diamond-splitter's table. The reader will see on the left the bluntedged steel rulers and the iron rod, somewhat in the shape of a double cone, which serves as a hammer; on the right, a saucer containing diamonds, and supporting a pair of pincers, and a lamp; in front, a handle having the sharp-edged cutting diamond attached, and, standing upright, the wooden implement which supports the diamond intended to be split; in the background is a globe of water for concentrating the light at such points as more particularly require it.


From the splitter the diamond passes to the cutter.

At first sight the work appears to be exactly the same as at the table of the splitter. The cutter has two diamonds attached by cement to wooden handles, and the same sort of a box as the splitter has, to receive the diamond-dust. But the process is essentially different. Instead of cutting a notch in one of the diamonds, the cutter is slowly and laboriously grinding the two together in that mutual manner which accomplishes the smoothing of both stones. He is putting in practice the famous discovery which Louis de Berquem is falsely said to have made by chance, and, from the primitive form received from the splitter, he is shaping the facets of the brilliant or the rose.

The work requires great muscular force, and the hands of the cutters have to be supported by gloves--we might almost call them cases--of stiff leather. These gloves are seen in Fig. 117, which represents the tools necessary to the work-table of the cutter.

A diamond, in the hands of the cutter, has not yet become an object of beauty; it has no lustre or transparency, and is even more unpromising in aspect than the rough diamond. The adamantine lustre, which is one of its special beauties; its transparency so pure; its refraction so powerful--all this is given to the diamond in the third phase of the cutting operation; and this phase belongs to the polisher.

The work of the cutter is not confined to the removal of the outer crust of the stones--he gives them the definite form which they are to preserve. If the stone is thick enough to produce a brilliant, he forms first the table, then the collet, and successively all the facets of the pavilion and the crown. It is easily seen that in all this labour a great deal of latitude is left to the cutter; but, as the final weight, and consequently the value of the stone, depends in a great measure on his skill, it is only tried workmen that are intrusted with valuable diamonds, such as those of larger size than four hundred to the carat. Smaller stones are made up in lots and delivered to the workmen after having been weighed.

So long as the diamond-cutter is engaged on a piece of work he shuts up the stones every evening in a little iron coffer provided with a padlock, of which he keeps the key. All these coffers, each with its number, are shut up after working hours in a large strong safe, and distributed to the workmen every morning. When the work is finished the large stones are weighed singly, the small stones in the lots, to see what the loss has been, and, according to the extent of this, the payment is greater or less. If a stone is found to be wanting in any of the lots, the workman has to pay a fine much greater than the value of the stone. As a brilliant of five hundred to the carat, or still more, a rose of a thousand to the carat, are very small objects, it often happens that they are lost in the course of the manipulations they have to pass through. The floor, and the dust upon it, are then subjected to a most minute examination, in which a long silken broom is used.


The polishing comprehends two distinct operations--the setting, and the polishing properly so called.

The setter has at his command a furnace filled with burning charcoal. His work is to solder the diamond into a quantity of alloy resting in a brass or copper cup, which has attached to it a rod for holding it by. The alloy consists of a mixture of tin and lead, which, when pressed into the cup, gives to the whole the form of an acorn, with the diamond as its apex. This soldering is no easy task. There are sixty-four distinct surfaces to be smoothed in the brilliant, and each of these must be properly adjusted in the burning mould. It would seem that the fingers of the setters are fire-proof, for it is with their fingers that they adjust the setting of the metal around the diamond; and when, after its manipulation, the alloy is plunged into water to be cooled, the cloud of steam that arises attests the painful temperature to which the hand of the workman has been subjected.

The diamond, set as the apex of the acorn-shaped lump of metal, which again rests in a brazen cup with unyielding stem, is given to the polisher.

The polishing-rooms are the most interesting apartments of the great establishments for diamond-cutting, such as that of Mr. Coster at Amsterdam. Before revolving steel disks, that are running scrupulously parallel with the floor, and turning noiselessly with a speed of two thousand revolutions to the minute, are numerous workmen intent upon their task.

The eyes of these polishers seem of little use compared with their sense of touch, which has been exquisitely educated. It is by the instinct of their finger-ends that the point of the diamond--kept constantly wet with mingled diamond-dust and olive-oil--is adjusted with determinate exactness of position, to the face of the revolving disk. It is clamped in a wooden rest, and the pressure is regulated by leaden weights, so that the diamond just touches the flying wheel. To the casual observer the polishing art seems to be one requiring little skill or intelligence, but to acquire proficiency in the work requires years of assiduous toil.

From generation to generation the trade has been carried on, and the patient and monotonous toil and technical skill inherited and acquired by the finished workman is sure to be rewarded at last by a glittering surface from the hardest stone.

Sometimes months, and even years, are required for the perfecting of single stones. African diamonds are said to be particularly hard and difficult to polish; but, in the end, the most hopelessly resistant gem yields to the indefatigability of man.

In Fig. 120 are shown some of the objects connected with the polishing of diamonds. In the background towards the left the polishing wheel of steel is seen, and scattered over the table three of the copper cups, filled with alloy. The implement near the centre of the table, with the two upright pieces or feet at the left end of it, is for holding the diamond on the wheel during the operation of polishing. For this purpose it has a kind of vice at the end, in which the tail or stem of the copper cup is tightly screwed, and the whole then forms a sort of tripod, the cup which carries the diamond forming the third foot. The nut of the screw, and the key for turning it, are seen at the head of the implement. Its use will be understood from the cut showing the polisher at work (Fig. II9).

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