The New York Times, July 19, 1867:|
ON DIAMONDS.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.
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 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.
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