gemstonesonline.org

Antwerp and Amsterdam regain their importance

In 1940, these centers were over-run by the Germans, and the skilled craftsmen were obliged to flee as refugees to various parts of the world. England, the U.S.A., and Israel were among the countries which benefitted by the influx, and before long, the lapidary industry was established on a small scale in various new countries. It seems that, although many of these victims will remain in their new homes, both Antwerp and Amsterdam will regain their previous importance. The Belgian and Dutch Governments do not want to lose this profitable industry, and most of the factories are working now. Antwerp recovered more quickly than Amsterdam since it suffered less from war damage, and in 1947, some 17,000 workers were already being employed on cutting all sizes of gem quality stones. The rough material is received from the Diamond Trading Co., in London, and the finished stones are exported to London and New York.
Lapidary work in England is confined to a comparatively small number of firms, and up to recently most of the work was connected with larger and finer stones and the re-cutting of old or “native cut” stones. Since 1940, however, the industry has expanded greatly and a number of foreign cutters were employed during the war years, chiefly in the cutting of industrial diamonds, a valuable accessory in all kinds of war machinery. In 1941, about 250 men were employed in Great Britain on diamond cutting, this being an unusually high figure. But the succeeding years saw a great increase, 600 workers being employed in 1942. In June of that year, the cutting of gem diamonds was entirely prohibited in Great Britain, except under license, and almost all the workers were employed on industrial stones. Factories were established in towns outside of London, and workers were busy in such towns as Bangor, Brighton, and Leamington Spa, producing material for the war.

Dutch and Belgian firms using diamonds

For some years prior to 1939, an increasing number of Dutch and Belgian firms were sending a proportion of their rough material to. Idar-Oberstein, Briicke, Hanau, and to other cutting centers in Germany. Here, the work was done on a commission basis since labor was cheaper in Germany. But Antwerp probably cut the bulk of the world’s supply of rough diamonds, and in that city some 30,000 cutters were normally employed, although Belgium itself purchased only about one per cent of the stones cut. As a rule, smaller stones were cut in this city, and the labor charges would amount to 60 per cent of the value of the finished product. In 1929, cut diamonds to the value of about $33,600,000 (£12,000,000) were exported from Antwerp.
Amsterdam employed about 6000 cutters, who mostly specialized in the cutting of larger stones, in which the labor represented one to five per cent of the value of the finished gem. Certain processes in lapidary work were also undertaken. Amsterdam has its Diamond Exchange, a building where important transactions lire operated by its members. Its Union of workers was world renowned before the industry was disorganized by war. At Antwerp, a Diamond Union was formed in 1937, its objects being to co-operate all diamond organizations, and also to develop the sale of diamonds by propaganda to the general public.

Polishing the stones

For polishing agate, lapis lazuli, turquoise, and malachite, beechwood rollers faced with soft leather are often used. These revolve at about 200 to 400 revolutions per minute. Chinese jade is polished with silicon carbide wheels, and lubricated with weak vinegar. Opal is best polished with leather discs coated with tripoli, which is really a finely grained silica, and obtained chiefly from the U.S.A. Rotten stone is a residual product derived from the weathering of siliceous clayey limestone. It is soft, friable, grayish-brown in color, with a fine, earthy texture. In chemical composition, it varies, but it is largely composed of silica, with some alumina, carbon, iron oxide, and lime.

For very many years up to 1939, the great majority of gem stones other than the precious varieties was cut in Germany. During the war years, few stones for jewelry were fashioned as all efforts were concentrated on producing material useful for war Industries. But a gradual resumption to more normal conditions has taken place, although various financial restrictions between  some countries and the lack of rough material has made progress slow.

Sawing of diamonds

The next operation is sawing, which divides up the rough material to the best advantage. Sawing may be necessary to obtain the largest possible stone from the given piece of rough if this is flawed, for cleavage might not obviate the flawed portion. This process is carried out by means of a thin copper or copper bronze disc, about four to five inches in diameter, the thin edge of which is kept supplied with diamond dust mixed with oil. This is applied with a small roller as a paste. The rough stone is set in cement and held between two holders, while the copper disc revolves vertically at a speed of about 1,500 to 5,000 revolutions a minute.
The large face obtained by sawing is used as the table of the stone, and further work is carried out on this basis. Lately, the process of sawing has been speeded up by the use of very thin blades which are rotated at high speeds. But thin discs of a phosphor bronze or copper are still used. The old fashioned method of bruting, by which two diamonds were rubbed together to obtain a rough shape or rough facets, and to remove corners and edges of crystals, is now seldom used. Special bruting machines are in use, in which the cutting agent remains another diamond.

Grinding, by which the facets are evolved, requires a light and delicate touch as well as good eyesight. Flaws may develop into serious cracks with undue pressure, while a slight variation in the degree of hardness within the same stone, a not infrequent occurrence, calls for extra care. In many flat, triangular stones, a vein may be found which runs across the polishing grain. This vein is termed a “naat,” and such specimens require very careful cutting. The process of cutting reveals faults; what seems to be a perfectly white stone in the rough may develop a slight tinge of color, a factor which has a great bearing on the value of the stone. Many crystals, when first found, have a very thin, transparent coating over their surfaces. This coat tends to neutralize the color in the body of the stone, which cutting and subsequent polishing reveals.

Cutting of diamonds

The cutting of diamonds is quite a separate industry from that of the cutting of the so-called “colored stones,” that is, the other precious varieties, and also from semi-precious stone work. Despite various developments and enterprises elsewhere, Antwerp and Amsterdam were by far the most important diamond cutting centers up to the year 1939, and the Idar-Oberstein district in Germany was preeminent in the cutting and marketing of semiprecious stones. The artificial staining of agates, of which we shall read later, and a considerable production of synthetic stones (but not pastes) was also carried out in the Idar-Oberstein and neighboring country. Waldkirch, Pforzheim (largely destroyed by Allied bombing in 1944), Briicke, and Hanau were other important centers in Germany for this work, and a very large proporton of the, world’s supply of semi-precious stones was fashioned here. The years following 1939 saw the world in a state of conflict and chaos, and for some time no systematic working of gem stones was done in any country, except perhaps in the U.S.A., where cutting establishments were increased on account of the influx of many European refugees. As industrial diamonds were considered of great importance to the war machine, these were produced wherever possible under government control.

Waste Material from diamonds

Waste material from diamond cutting is used for industrial purposes, such as drills and polishing material. Diamond powder, which was originally the waste from the processes of cleaving and bruting crystals, was used only for grinding and polishing. But now it is considered to be the best abrasive on account of its great hardness and sharp edges. Suitable material is now crushed for this purpose. Faulty material discarded in the fashioning of other stones is mostly useless; a little corundum and garnet are used for polishing and drilling, chiefly in the East. All stones of appreciable worth are valued on the basis of weight, so not only must the best results be obtained from the rough stone in hand, but unnecessary loss of weight must be avoided.

Many stones which come from the East, such as Ceylon, India, and Siam, are cut in their country of origin. Such stones include jade, garnet, moonstone, ruby, sapphire, zircon, spinel, and chrys-oberyl. But in most instances, especially with the transparent stones, re-cutting is essential when they reach the West since the facets are generally unsymmetrical and their proportions wrong according to modern ideas. These so-called “native cut” stones are considered only with a view to retaining as much weight as possible, so although the color may be brought out, many of the imperfections within the stone are retained to its detriment. Jade is
an exception. This stone is almost exclusively cut in China, and the skill shown in working it, especially in the carving, far exceeds anything that has been done elsewhere.

The period 1914 to 1918

The period 1914 to 1918 was a difficult one on account of the lack of coal supply, but a solution was found in electricity, which power the entire industry now uses in Amsterdam. There was progress in the next twenty years, but 1940 saw a complete disorganization of the Low Countries on account of the German invasion and occupation. Skilled workers fled to every country which would accept them, and the few that were left were obliged to work on industrial stones for the German war machine.

The cutting of diamond requires considerable skill, accuracy, and a fine sense of touch, as well as much patience. A knowledge of the effects of the reflection and refraction of light is necessary, and on this is based the number of facets and the angle of their inclination to each other. With colored stones, dichroic effects also have to be considered, but the size of the facets and their mutual inclination are not so important as with diamond. The skilled cutter constantly checks the progress of his work by eye only, with the aid of a loupe or eye-glass, and very rarely will he take any angular measurement by any instrument. Machines for the mechanical faceting of diamond and other precious stones have been devised, but they have, as yet, been very rarely used.

Abrasive property of diamond

It was not until the Fifteenth Century that the abrasive property of diamond used for manufacturing diamond engagement rings was discovered and used. The attempt to cut and polish this stone by any other stone or material had always failed, and naturally so, since diamond is the hardest substance known. Subsequently, the cleavage property of diamond became known, and this was of enormous value in dividing up the rough stone in place of the older method of laboriously slitting by hand. The introduction of modern appliances with the use of electricity further facilitated the work, and with the investigation and knowledge of the optical properties of this remarkable stone, the present forms of cutting, and especially the so-called brilliant  cut, were evolved to show its full splendor. To Louis van Berguen, a citizen of Bruges, is ascribed the discovery of the art of cutting and polishing diamonds in the year 1456. The “brilliant” form of cutting was discovered much later, toward the end of the Seventeenth Century, by Vincenzio Perruzzi, while he was experimenting with colored stones.

The craft, as an industry, dates from about the year 1580, and during” the Seventeenth and Eighteenth Centuries it expanded considerably in Amsterdam. In many respects, early conditions of working were crude, a young girl often being hired for a few pennies per day to turn the polishing wheel. In 1822, the factories used horse power for the first time, and in 1840 or thereabouts, the first steam driven mill was opened. A model factory was built in 1886 by De Vooys in which small brilliants were cut, and from then onwards, the home industry gradually disappeared, and factory regulations with all their advantages to the employees have since operated.

The Egyptian method of drilling

The Egyptians also knew of a method of drilling, which was effected by a tubular drill, a hollow copper tube, and this was rotated either by rolling between the hands or by means of a handle, an abrasive powder being used at the same time. A copper or stone point was also sometimes used, as well as a crescent shaped flint fixed in an eccentric handle. The abrasive powder was probably very finely ground quartz sand, aided by water. Even today, these principles are followed in the main by many lapidaries in the East who do not possess the modern advantages of electric power, modern abrasives, and improved tools which are in use elsewhere.

The cutting of diamonds probably originated in India over a thousand years ago, and in due course the art passed to Constantinople and then to Venice. In the Fourteenth Century, it is known that lapidaries were at work in Nuremberg, Paris, and Bruges, but religious persecution drove the cutters to Antwerp and Amsterdam, where most of the work has been carried out for so many years. There is no doubt that, for centuries, precious stones such as diamond, emerald, and ruby were kept in the same form as that in which they were found, and the first attempts at cutting and faceting were aimed at improving the natural faces of the crystals. Flaws were covered by small facets, and many of the old Indian stones remained like this for centuries before they were re-cut. Many of these were, however, engraved on the surface with some device, for the craft of engraving gems dates back to Babylonian times.

Carbonado - the toughest diamond

Carbonado, which comes mainly from Brazil, is the toughest variety of diamond, but it is far less plentiful than boart. Corundum, when used as an abrasive, is dull gray or brown in color, nontransparent, and it is largely imported from the Transvaal. Much’of this is exported to the U.S.A. for use in grinding wheels.
Emery is a close mixture of granular corundum and magnetite. Deposits occur as pockets in crystalline limestone, or as residual deposits after the removal by weathering of such rocks. This material is found in the island of Naxos (Grecian Archipelago), Turkey (the province of Aiden in Asia Minor), and in the central Urals (U.S.S.R.). Those garnets which include iron are chiefly used for grinding and polishing, and the most important deposits are found in the Adirondacks, U.S.A.

The working of stones by which their natural surfaces are improved dates back to many centuries. The art reached a high standard in Egypt over 5000 years ago, and it is known that the Egyptians worked comparatively hard stones, such as quartz, by pounding and rubbing with a stone held in the hand. Sawing was carried out by means of a copper blade, together with the help of an abrasive power. These processes are represented in many tomb paintings.