DIAMOND DUST 27 



also for piercing holes in artificial enamel teeth, or any vitreous substances, however 

 hard. 



The following description furnished to Mr. Tonnant, by Messrs. Garrard, of tho 

 cutting of the Koh-i-noor will fully explain the peculiar conditions of the process, 

 and also show that there are some remarkable differences in the physical condition of 

 the gem in its different planes. The letters refer to the cut of the Koh-i-noor, fig. 602, 

 (p. 23): 



' In cutting diamonds from the rough, the process is so uncertain that the 

 cutters think themselves fortunate in retaining one-half the original weight. The 

 Koh-i-noor, on its arrival in England, was merely surface cut, no attempt having been 

 made to produce the regular form of a brilliant by which alone lustre is obtained. By 

 reference to the figures, which are the exact size of the Koh-i-noor, it will be clearly 

 understood that it was necessary to remove a large portion of the stone in order to 

 obtain the desired effect, by which means the apparent surface was increased rather 

 than diminished, and the flaws and yellow tinge were removed. 



' The process of diamond cutting is effected by a horizontal iron plate of about 

 ten inches diameter, called a schyf or mill which revolves from two thousand to three 

 thousand times per minute. The diamond is fixed in a ball of pewter at the end of 

 an arm, resting upon the table in which the plate revolves; the other end, -at which 

 the ball containing the diamond is fixed, is pressed upon the wheel by moveable weights 

 at the discretion of the workmen. The weight applied varies from 2 to 30 Ibs. accord- 

 ing to the size of the facets intended to be cut. The recutting of the Koh-i-noor was 

 commenced on July 16, 1852, His Grace the late Duke of Wellington being the first 

 person to place it on the mill. The portion first worked upon was that at which the 

 planes p and F meet, as it was necessary to reduce tho stone at that part, and so to level 

 the set of the stone before the table could be formed ; the intention being to turn the stone 

 rather on one side, and take the incision or flaw at E, and a fracture on the other side of 

 the stone, not shown in the engraving, as the boundaries or sides of the girdle. The 

 next important step was the attempt to remove an incision or flaw at c, described by 

 Professor Tennant and the Eev. W. Mitchell as having been made for the purpose of 

 holding the stone more firmly in its setting, but pronounced by the cutters (after having 

 cut into and examined it) to be a natural flaw of a yellow tinge, a defect often met with in 

 small stones. The next step was cutting a facet on the top of the stone immediately above 

 the last-mentioned flaw. Here the difference in the hardness of the stone first manifested 

 itself ; for while cutting this facet, the lapidary noticing that the work did not proceed so 

 fast as hitherto, allowed the diamond to remain on the mill rather longer than usual, 

 without taking it off to cool ; the consequence was, that the diamond became so hot from 

 the continual friction and greater weight applied, that it melted the pewter in which it was 

 imbedded. Again, while cutting the same facet, the mill became so hot from the ex- 

 treme hardness of the stone, that particles of iron mixed with diamond powder and oil 

 ignited. The probable cause of the diamond proving so hard at this part is, that the 

 lapidary was obliged to cut directly upon the angle at which two cleavage planes meet, 

 cutting across the grain of the stone. Another step that was thus considered to be 

 important by the cutters was removing a flaw at G. This flaw was not thought by 

 Professor Tennant and Mr. Mitchell to be dangerous, because if it were allowed to run 

 according to the cleavage, it would only take off a small piece, which it was necessary 

 to remove in order to acquire the present shape. The cutters, however, had an idea 

 that it might not take the desired direction, and, therefore, began to cut into it from 

 both sides, and afterwards directly upon it, and thus they succeeded in getting rid of 

 it. While cutting, the stone appeared to become harder and harder the further it was 

 cut into, especially just above the flaw at A, which part became so hard, that, after 

 working the mill at the medium rate of 2,400 times per minute, for six hours, little 

 impression had been made ; the speed was therefore increased to more than 3,000, at 

 which rate the work gradually proceeded. When the back (or former top) of the 

 stone was cut, it proved to be much softer, so that a facet was made in three hours, 

 which would have occupied more than a day, if the hardness had been equal to that 

 on the other side ; nevertheless, the stone afterwards became gradually harder, especi- 

 ally underneath the flaw at A, which part was nearly as hard as that directly above 

 it. The flaw at N did not interfere at all with the cutting. An attempt was made to 

 cut out the flaw at A, but it was found not desirable on account of its length. The 

 diamond was finished on September 7th, having taken thirty-eight days to cut, working 

 twelve hours per day without cessation.' The weight of the Koh-i-noor since cutting 

 is 102 carats. 



DIAMOND BORER. See BOEING. 



DIAMOND BORON. See BORON. 



DIAMOND DUST. The use of diamond dust within a few years has increased 

 very materially, on account of the increased demand for all articles that are wrought 



