POLISHING COLOURED STONES
PLATE IX
FACETING MACHINE
As in the case of diamond, the lapidary judges of the position of the facet entirely by eye and touch, but a skilled workman can develop a facet very close to the theoretical position. During recent years various devices have been invented to enable him to do his work with greater facility. A machine of this kind is illustrated on [Plate IX]. The stone is attached by means of cement to the blunt end, d, of the holder, b, which is of the customary kind, while the other end is inserted in a hole in a wooden piece, a, which is adjustable in height by means of the screw above it. The azimuthal positions of the facets are arranged by means of the octagonal collar, c, the sides of which are held successively in turn against the guide, e. The stand itself is clamped to the bench. The machine is, however, little used except for cheap stones, because it is too accurate and leads to waste of material. Stones are sold by weight, and so long as the eye is satisfied, no attempt is made to attain to absolute symmetry of shape.
The pictures on [Plates X–XIII] illustrate lapidaries’ workshops in various parts of the world. The first two show an office and a workshop situated in Hatton Garden, London; in the former certain of the staff are selecting from the parcels stones suitable for cutting. The third depicts a more primitive establishment at Ekaterinburg in the Urals. The fourth shows a typical French family—père, mère, et fils—in the Jura district, all busily engaged; on the table will be noticed a faceting machine of the kind described above. In the fifth picture a native lapidary in Calcutta is seen at work with the driving bow in his right, and the stone in his left, hand.
A curious difference exists in the systems of charging for cutting diamonds and coloured stones. The cost of cutting the latter is reckoned by the weight of the finished stone, the rate varying from 1s. to 8s. a carat according to the character of the stone and the difficulty of the work; while in the case of diamonds, on the other hand, the weight of the rough material determines the cost, the rate being about 10s. to 40s. a carat according to the size, which on the average is equivalent to about 30s. to 120s. a carat calculated on the weight of the finished stone. The reason of the distinction is obviously because the proper proportions in a brilliant-cut diamond must be maintained, whatever be the loss in weight involved; in coloured stones the shape is not of such primary importance.
PLATE X
