There are diamonds of all shades, the white diamonds being the most valuable. There are, however, on view in M. Coster's establishment, tinted brilliants and dark-blue stone of exceptional beauty.
The New York Times, July 19, 1867:
Translated for the Times from the Journal des Debats
A small brick building, lighted by large windows and topped with a high chimney, stands in the garden reserved for the Kingdom of the Netherlands, and represents, on a small scale, the factory owned by M. Coster, in Amsterdam, on the banks of the Amstel, and tenanted daily by 450 workmen.
This factory is the largest diamond-cutting establishment in the world.
The branch of industry giving employment to diamond-cutters is a peculiar one, and seems to have been naturalized in Holland.
The gems reach the Netherlands in the rough--glitterless and almost opaque--and are subsequently exported as transparent as a dewdrop, cut into numberless facets, and glistening and dazzling to look upon. The Kohinoor and the Star of the South--two trifles worth thirty millions of francs--were cut by M. Coster's workmen.
Everyone knows the real nature of the diamond, which is pure carbonic gas in a solid state. Besides its extreme density, clearness and refracting properties, it shares as the natural a property that rarely deceives, that of coldness.
An experiment can easily be made by tasting first a piece of straw and then a diamond; by the cold feeling produced upon the tongue the real diamond can be readily distinguished from the valueless pebble...
Such a test need not be applied within the limits of the diamond-cutting establishment at the Exposition, for the gems on exhibition are all of the first water. M. Coster has gathered together different specimens of diamantiferous earth, and his workmen perform, in the presence of crowds of visitors, all the operations incidental to diamond-cutting.
The larger portion of the specimens now brought to light are obtained from Brazil. One can examine, in cleverly-contrived showcases, the different elements composing ca cascatho, that is to say, the kind of soil in which diamonds are usually found. Diamantiferous earth is generally a conglomeration of quartz, platina, nugget gold, flint, iron, jasper, and diorites, mingled together and forming an almost solid mix. A fragment of diamantiferous earth might be mistaken for a piece of half-cooked nougat. Two specimens of the kind are at the exhibition, containing some small diamonds embedded in rock-crystal; the amateur of gems must have keen eyes to discover them.
Jewelry ad from the June 17, 1936 NY Times
The largest black diamond ever discovered is now at the Exposition. It is peculiar, because despite its blackness, it is perfectly transparent, and being skillfully cut, refracts the light with wonderful effect. This is the more extraordinary from the face that it is usually impossible to cut black diamonds; they are generally pounded in a steel mortar, and subsequently used as diamond-dust to polish softer gems. M. Coster has in his collection a number of these truly adamantine stones, which resemble scraps of blackened copper...
In a small showcase divided into three compartments is to be seen a number of rough diamonds from the mines of Rio, Bahia and Cuyaba. The products of Rio mines look like tarnished fragments of gum arabic; while those from other parts of the country are more flat and brilliant, and are sometimes tinted. In that state diamonds are placed in the Brazilian market, after having been freed from outer impurities by several successive washings. The diamond in that state is worth about 11 francs per carat; it will be valued at about 250 francs when cut, and after having been submitted to a series of operations, all of which are based upon the experiments made by Louis Bergeum in 1476, and can be summed up in the words: diamond cut diamond.
Diamonds are generally cut either as rose diamonds or as brilliants.
The rose diamond is flat underneath; its upper part rises as a "cupola" divided into four and twenty facets; the topmost portion of the cupola is formed by the junction of six triangles.
The brilliant is divided into two parts, known respectively as the "crown" and the "pavilion." A plain surface called the "tabula" surmounts the crown; under the pavilion is another plane, known as teh "breech." When a brilliant is skillfully cut, the pavilion is twice the depth of the crown; besides, the axis passes through the central points of the tabula and the breech. The tabula should be five or six times wider than the breech. A more or less strict observance of these proportions is indicated by the varying brightness of the sparkle. A brilliant has two parallel faces, eight sides tending toward the tabula and eight sides tending toward the breech. Each of these sides is provided with four facets, so a perfect brilliant must have sixty-four facets, besides the breech and tabula.
After the rough stone has been carefully examined, it is set aside to be transformed, according to its dimensions and shape, either into a brilliant or a rose diamond. Subsequently the gem is entrusted to a special workman, who "cleaves" it, or cuts it with the grain. By this process it is freed from any apparent roughness and from the stains which sometimes deface the finest stones. Great judgement and experience are needed to perform this operation, for the value of the diamond is usually dependent upon its success. The workman must examine the flexures of the gem to determine the precise location for the breech and the tabula, which from the two extremities of the pivot around which are to gravitate the luminous facets.
Once the points fixed upon, the workman places the gem in a bed of peculiar cement, which is malleable when heated and easily hardened by cooling; the cement is spread upon a wooden mandrel.
A small diamond blade, very thin but very hard and sharp, is then imbedded in the cement, brought to bear upon the diamond, and moved to and fro, like a saw, under a heavy pressure.
Soon a slight dent is made in the gem, a well-tempered chisel is substituted for the diamond blade, the workman gives the chisel a blow, the stone is cut in twain, and the cleaving process is terminated.
The second operation is performed by a workman who sets himself on a high chair and rests his elbows on a table. In either hand he holds a mandrel, a diamond being embedded in the cement of each. The workman's hands are encased in thick gloves, for the task he has to accomplish is tedious and fatiguing, and exacts a considerable expenditure of strength.
Bringing the two mandrels into contact the cutter rubs the stones against each other with a measured violence that sets his whole body in motion. Slowly the gems lessen in size, and assume the intended shape. When a brilliant leaves the hands of the diamond-rubber, it has the appearance of two truncated pyramids, each soldered to the other by its base. But who would recognize the gem in that tarnished stome apparently covered with ashes?
All the imperceptible particles detached from the diamond by friction fall into a box on the table, and, passing through a copper-sieve with capillary holes, are carefully preserved, as constituting the diamond dust with which the stone, now dull and discolored, will, by-and-by, be changed into a glistening jewel.
For many years, and at no very distant date, diamond dust was considered a poison without a remedy.
After the diamond has been cleft, a workman solders it in an egg, the upper portion of which is a mixture of lead and tin, while the lower part is made of copper and supported by a short and stout handle. The whole contrivance looks like a metallic magnolia-bud grafted on a three-inch stem.
The solderer secures the handle of the egg in a vise and then brings the face of the stone, and only that part of it which is to be polished, to bear upon a horizontal table, upon which has been strewn diamond dust made adhesive by admixture with oil. The material of the table is iron, and must be neither too hard, lest it scatter the dust, nor too soft, lest the powder become ingrained into it. It revolves two thousand five hundred times per minute.
As soon as one facet has been ground the gem is unsoldered and resoldered again to admit of the cutting of another, and of the exposure in turn of each face of the stone to the action of the polishing machine. Great care must be exercised in cutting the facets of a diamond, for each facet must be of regular proportion. The workman must know the precise dimensions; no compass aids him, and as he see but one facet at a time he would be often apt to damage a gem if [not for] experience...
When a diamond has been soldered and unsoldered once for the tabula, once for the breech and once for each of the sixty-six facets, the work is done. The diamond-cutter has accomplished his task, and the jeweler must set out upon his. We are really indebted to Holland for the invention of a regular system of cutting, and it is thanks principally to the efforts of M. Coster that during the past few years such great progress in the art has been made.
The diamond trade is more extensive than one would suppose. An idea of the large amounts involved in its prosecution during the last eight years may be obtained from the subjoined statistics, indicative of the quality and value of the rough diamonds exported from Brazil to Europe within that space of time:
No. of Carats
All these diamonds, with very few exceptions, have passed through M. Costner's establishment before being put into circulation.
It is a comparatively easy task to cut stones of a certain size, but it is difficult to understand how mere dust can be submitted to all the regular processes. The standard weight for the diamond is, as is known, the carat. The carat was originally a seed which was used in India and on the shores of the Red Sea to weigh diamonds and pearls. The carat represents in avoirdupois weight only 20.275 parts of a gramme--there are 500 grammes to the pound--yet there are to be seen in M. Costner's show-cases diamonds weighing the one-thousandth part of a carat, which have been successfully cleft, polished and provided with twenty-four facets, a cupola and a base.
Cracks are not rare in a diamond of the first water; these defects are called "feathers." It may be here said that the famous diamond known as the Regent and worth about 15,000,000f. contains a feather in one of its facets. Yet for shape, clearness, brilliancy of size, the gem is the finest in the world.
While among the many curiosities in M. Costner's collection one must not overlook a marvelous piece of workmanship, a portrait engraved on a diamond. It is not, like the picture on a diamond-bee belonging to Queen Victoria, a mere outline, but an excellent likeness to the original, with all the hollows and relief clearly distinguishable. M.C.M. de Vries is the author of the work, in the accomplishment of which many diamond points were worn down, and no little time and labor expended.
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Classic Gem Articles:
Rubies, Sapphires, Emeralds 1895
Semi-Precious Stones 1896
Gem Cutting & Polishing 1896
Where Gems are Found 1904
Classic Diamond Articles:
On Diamond Cutting 1867
De Beers Diamond Mine 1888
Diamond Cutting Industry-Art 1895
Cutting the Cullinan Diamond 1908
Classic Pearl Articles:
Bahrein Pearl Trade 1914
Classic Watch Articles:
Making Watches in Waltham 1867
World of Watches