DIAMOND: CUTTING 243 



It has been stated by Tavernier that the custom of cleaving diamonds has been 

 practised in India since very early times ; in Europe, however, the art was acquired much 

 njore recently, and is said to have originated with the English chemist and physicist 

 Wollaston (1766-1828), of whom it is related that by cleaving away the faulty exterior 

 portions of a large diamond he was enabled to dispose of the stone at a considerable profit. 



Stones which, either by nature or by the hand of -man, have been given the shape of 

 an octahedron, have already the ground-form of the brilliant and can be at once faceted. 

 The work of grinding the facets is facilitated by a preliminary operation, which is entrusted 

 to special workers and is not performed in the process of cutting any other gem. This 

 operation, by which the shape and position of the facets are roughly marked, out, is known 

 as bruting, rubbing, or greying the stone. The stone to be bruted is fixed to a handle^ 

 and, with the exception of the area on which the facet is to be made, is embedded in cement, 

 or in a fusible alloy of lead and tin. This projecting portion is rubbed with a strong; 

 pressure upon the projecting portion of another stone similarly mounted and prepared, and. 

 thus a facet, in approximately the correct position and with a fairly even but rough surface^ 

 is developed upon each of the stones. The powder abraded from the two stones during the- 

 operation is carefully preserved for use in grinding. During the operation of greying,, 

 which, by the way, derives its name from the grey metallic appearance of the facets so. 

 made, any over-heating of the stone by friction must be carefully avoided, since it leads to. 

 the development of " icy flakes ■" in the interior of the diamond. The operation is attended! 

 by a peculiar grating sound, which is said to be so characteristic that by this alone the: 

 possessor of a practised ear can determine whether the two stones which are rubbedl 

 together are diamonds or some less hard gems. 



At the completion of the first stage of the operation the stone is removed by warming 

 the cement or alloy, placed in another position, and the remaining larger facets successively 

 marked out in the same way. The smaller facets are not so marked out by a preliminary 

 operation, but by the subsequent process of grinding. When ready for the grinding 

 process the stones are bounded by a number of fairly even, rough faces, with a grey, some- 

 what metallic lustre ; they have no longer the appearance of diamonds, but resemble duH 

 gi-ey metallic bodies with the general contours of the form of cutting the stone is finally 

 to take. 



In the combined process of grinding and polishing, the preliminary disposition 

 of the facets, which may be slightly incorrect, is rendered strictly accurate by the completion 

 of the grinding, their rough surfaces are rendered smooth and shining, and the smaller 

 facets are added. The grinding process is the same as in xhe case of other gems as already 

 described, the diamond being imbedded in the fusible alloy of a dop and placed on the 

 grinding disc. Since in the grinding of diamonds the disc must be charged with diamond 

 powder, which of course has the same hardness as the stone itself, the operations of grinding 

 and polishing take place simultaneously, and any separate polishing process is superfluous. 

 Any dirt or foreign matter which may adhere to the stone after the process of grinding is 

 removed by treatment with fine bone-ash or tripolite. 



In the process of grinding it is by no means immaterial in which direction the grinding 

 disc moves across the facet which is being worked. Owing to the fact that the diamond, as 

 well as other precious stones, has a difierent degree of hardness in different directions, the 

 grinding of its facets can be accomplished with comparative ease in some directions, while 

 in others the process is extremely tedious. To avoid injury both to the stone and to the 

 grinding disc, the diamond must be ground " with the grain " ; and the operator ought to 

 make himself familiar with these directions of least resistance, otherwise his work will be 



