DIAMOND-CUTTING. 



207 



prismatic spectrum. All limpid and wliite gems must be cut accord- 

 ing to this rule, but with colored stones the case is different, for here 

 perfection of color is to be attained, and brilliancy is a secondary con- 

 sideration. Hence, a fine ruby or sapphire may be decidedly thin, and 

 yet be a gem of great beauty and value. 



Fig. 1. Stewart Diamond. Rough South 

 African Crystal, weight, 288>^ carats. 



Fig. 2. Star of the South. Rough 

 weight, 254;^ carats. 



The process of rifting diamonds by splitting them in their cleavage- 

 planes was known long ago to the Hindoos, but was forgotten to 

 modern lapidaries till revived by Wollaston not many years ago. By 

 this means masses of the crystal may be removed to escape a flaw or 

 remove a spot. Some diamonds of the spheroidal form are deficient 



Fig. 3. Mattam Diamond, Borneo. 

 Rough weight, 367 carats. 



Fig. 4. The Koh-i-noor before Recutting. 



in cleavage-planes, and are quite impracticable for cutting; others 

 have a concentric arrangement of the planes of cleavage, as though 

 crystallization radiated from the centre, and it is very difficult to 

 polish them. The Hindoos avail themselves of the natural cleavage 



