CATALOGUE OF GEMS AND PRECIOUS STONES. 



143 



girdle, one-third, and from the girdle to the culet two-thirds of the 

 total. The diameter of the table should be four-ninths of the breadth 

 of the stone. When applied to other stones these proportions are 

 more or less modified to suit their individual optical constants. 



DOUBLE BRILLIANT CUT. 



The double brilliant, or Lisbon cut, is a form with two rows of 

 lozenge-shaped facets, and three rows of triangular-shaped facets, 



Fig. 17.— The double brilliant. Top (a), side (6), and back (c) views. 



74 in all. The figure shows top (a), side (b), and bottom (c) views 

 of this fashion. 



HALF BRILLIANT CUT. 



The half brilliant, single, or old English cut is the simplest form of 

 the brillliant, and is generally employed for stones too small to admit 



Fig. IS.— The half brilliant. Top (a), and side (6) views of the half brilliant. In c the 



TOP IS CUT IN THE FORM OF A STAR, THEN CALLED ENGLISH SINGLE-CUT. 



of numerous facets. The figure shows top (a) and side (b) views of 

 this style of cut. Occasionally the top is cut so as to form a star (c 

 in fig. 18) and then called English single-cut. 



Fig. 19.— The trap brilliant. Top (a), side (6), and back (c) views. 

 TRAP BRILLIANT CUT. 



The trap brilliant, or split brilliant, differs from the full brilliant 

 in having the foundation squares divided horizontally into two tri- 

 angular facets, making 42 in all. 



