We have thus seen that the three operations in the process of diamond cutting are entrusted to as many classes of skilled workmen, namely cleavers, bruters, and grinders or polishers.
The order in which the facets of a brilliant are ground has also a certain importance. Starting from the octahedral ground-form, the table and culet are in every case first developed. The correct proportions of a brilliant are attained by grinding, cleaving or cutting away five-ninths of the upper half for the table, and one-ninth of the lower half of the stone for the culet, the upper portion of a perfect brilliant being one-third, and the lower being two-thirds of the whole thickness of the stone from table to culet.
Some rough stones are of such a shape that they cannot be cut into the usual brilliant form, but are given an oval or triangular outline; in this case, the method of procedure described above requires a slight modification, as also when the stone is to be cut as a rose or In some form other than the brilliant. In the latter cases the cleavage of the stone does not play so important a part, but otherwise the mode of procedure is much the same.
In past times the diamond-cutting industry has centered now round this town, now round that. The important invention ascribed to Ludwig van Berquen was made in 1476 at Bruges; in the fifteenth and sixteenth centuries, however, most of the work was done in Antwerp, where the workers of L. van Berquen had settled. Later on Amsterdam became the center of the industry, and through many vicissitudes this city has retained its supremacy up to the present day. In Amsterdam there are now many diamond-cutting establishments, large and small, fitted up with all the modern technical appliances. The industry gives employment to many people, most of whom are Jews. Amsterdam, however, no longer monopolizes the industry, for skillful cutters are now to be found in Antwerp, Ghent, Paris, St. Claude in the French Jura, London, and specially in Germany, more particularly at Hanan; diamond-cutting works are also to be found at Berlin and at Oberstein on the Nahe, a town which has long been well known as the center for the working of agate and other varieties of quartz. In America the diamond-cutting industry has been introduced at Boston. India specializes in cutting small stones, the same as Israel. But Amsterdam still holds the lead, and the largest and most valuable stones are always entrusted to the cutters there, who are held to be the most skilful and who best understand how to provide quite small stones with regularly arranged facets.
While the softer precious stones are often submitted to the operation of engraving, the diamond is very rarely so treated. Whether diamonds were engraved at all by the ancients is a matter open to grave doubt; only a few engraved diamonds belonging to more recent times are known; one of these bears the portrait of Don Carlos, and another was engraved with the Spanish arms for Charles V. The engraving of the diamond is never attempted at the present day, since the result of such attempts is in no way commensurate with the labor expended. That the art was not entirely unknown in the Orient is evidenced by the existence of a beautiful Indian octahedron of 30 carats, described by Boutan, one face of which was engraved with a devotional motto. According to G. Rose's account, some of the faces of the irregularly-formed diamond known as the "Shah", at one time in the Russian crown jewels, were engraved in Persian characters with the names of Persian kings. Two of tile faces of the "Akbar Shah," another large diamond, were engraved with Arabic inscriptions, but these, like the engravings on the "Shah," had to be sacrificed when the stone was re-cut.
Only rarely have diamonds been bored and threaded as beads; the art is said to be practiced up to the present day at Venice, in this city being the last remains of an old diamond-cutting industry which once flourished there. The boring is effected by the use of diamond powder, the perforation being started with a diamond point and continued with a steel point charged with diamond dust.
Diamonds: Large and Famous Properties Geology and Mining Cutting Diamond trade
Rafal Swiecki, geological engineer email contact
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