There was little or no incentive to polish and shape diamonds during the centuries that they were regarded as talismans. Those set in rings were usually natural octahedra and perhaps, in many cases, glassies with flat, highly reflective faces. The Indian lapidary work Agastimata, probably written in the fourteenth century, is the earliest record of the fact that diamonds can be finished by using other diamonds, but the author gave a warning that a diamond polished on a wheel would lose its magical powers. To grind diamonds with the use of a wheel or mill requires diamond powder, so presumably the first discovery was that diamond pieces could be pulverized into a fine dust. This invention was attributed by Robert de Berquen (wriung in 1661) to his ancestor Louis de Berquen in 1476, an untrue statement that has persisted for centuries.
Grinding, Cleaving and Cutting
Grinding and polishing diamond with diamond dust is a slow but reasonably flexible process because many different shapes or patterns of facets are possible. The diamond grinding wheel called the scaife was in use in the fourteenth century and if diamonds were ground before its introduction, the operation was probably carried out in the same way as other gemstones were ground at an early date, as shown in the book of Presbyter Theophilus of about the tenth century. A table facet was rubbed on gems other than diamond by using a sandstone, a lead table, and finally a goat skin with brick dust moistened by saliva.
The earliest known pictures of diamond polishing are obviously, because of the style, copied from a com- mon source. This was said to be Staendebuch by Most Amman of Nuremberg, 1568, though the originals have not been traced. The top illustration has a Dutch text and appeared in Menschelyke Bcczigheeden(HumanTradex"), published inHaarlem,1695.
The rough diamond, however dark, Receives in polishing all its lustre. Those of pure water, and large of body, are called a gem. The lower comes from a different Dutch text which may well be as old. It has been calculated that the woman turning the wheel has to produce nearlyt of a horsepower when the scaife is under load. In later pictures, the woman is sometimes assisted by a child. This engraving has been attributed to Jan Luiken, made in Holland about 1700. The text reads: "The Diamond-polisher' "These are drops from one source, the final poem just begun.' Man likes being clegant, With diamond stone, or ruby, So that his wealth can be praised It would be better if he started correctly, By first shining like the sun, That will be another beauty.
Cleaving is a very much more rapid method of shaping a diamond but is exceptionally limiting because only octahedral faces and forms can be produced. Although the first diamonds used in jewellery were 'point-cut', they were probably produced not by cleaving but by grinding and polishing the octahedral faces of a crystal at a slight angle. It is impossible to grind them flat as they are too hard. In any case, the art of cleaving was probably unknown at this early date. The first reference to cleaving appears to have been made by Tavernier when writing of tabular crystals found in the Indian Raolconda mines. He commented that Indians were more skilful than Europeans at cleaving. A major step in diamond shaping was the invention of bruting, usually described in the past simply as cutting (hence 'cutting and polishing' described the whole operation), which probably occurred in the late fourteenth or early fifteenth century. In bruting, a whole piece of diamond set in a stick, instead of diamond powder, was used as a tool to shape another diamond, also set in a stick, before faceting it. Sawing is a specialized form of grinding used to divide diamond crystals and probably followed bruting as a manufacturing method.
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