DIAMONDS — LOGIE 359 



are found in Nature as single crystals and seldom showing any sign 

 of having been previously attached to any matrix. Absolutely color- 

 less stones are not as coimnon as cloudy or faintly colored specimens ; 

 the most common tints are gray, brown, yellow, and blue- white. Much 

 more exotic colors are also sometimes found, and red, green, blue, and 

 black stones are know^n. When the diamond has been cut and polished 

 as a brilliant, it has 58 facets and in a tasteful setting is a tiling of 

 great beauty. Even people who do not long to possess diamonds are 

 seldom indifferent to their attractions. And this despite the fact that 

 diamonds and graphite are made of the same single element — carbon. 

 They are in fact different in appearance and characteristics only be- 

 cause the carbon atoms have been packed together in a slightly differ- 

 ent way. We shall return to this point later. 



There is art in the production of a gem stone. Nearly all the finest 

 jewels reach the lapidary as rough stones of typically octahedral shape. 

 The first task is to saw the diamond into two parts. Along certain 

 planes the sawing process is easy ; along others it is difficult. Simi- 

 larly when it comes to polishing the faces, which is done on a revolving 

 wheel impregnated with diamond dust (a method which was hit upon 

 shortly before Columbus discovered America), it is foimd that it can 

 best be done in certain directions rather than in others. The diamond 

 cutters speak of this as being due to the "grain" of the stone, and on 

 any face there are "easy" and "hard" polisliing directions which may 

 differ in their abrasive hardness by a factor of 10,000. All this has 

 been a matter of scientific study, and only recently and after centuries 

 of tradition, has the lapidary's art been changed to a science. 



Provided that the size of the diamond is convenient — and size, 

 or rather weight, is measured in carats with 142 carats to the ounce — 

 the cutter will divide the rough diamond into two parts by sawmg 

 along a plane parallel to the base of the two pyramids which form 

 the octahedron. The larger portion is the more economical to work 

 with. The corners are rounded off, then the bezel and the pavilion 

 are polished to make 58 facets in all. About half the weight will be 

 lost in the process, but the rather dull-looking stone has come to life 

 as a result. The unusual brilliance of a diamond is due to its high 

 refractive index (2.42) which makes the critical angle 24i/2°; the 

 very high dispei-sion of the diamond gives it the "fire" or display of 

 spectral colors. 



For centuries diamonds have been cut and polished using methods 

 similar to these and in the case of some of the great jewels which 

 have been in existence for hundreds of years, one is amazed at the 

 excellence of the work. Round these huge diamonds, which have 

 usually been the property of Idngs, there have grown many legends 

 partly of truth and partly of fiction. Perhaps the best known of 



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