CATALOGUE OF OEMS, 547 



V. THE CUTTING OF GEM STONES. 



The cutting- of ocin stones is neeessary for the complete deveU)p- 

 nient of those properties upon which their l)e!iut3' laroely depends. 

 Rarely does the oeni stone, as found in nature, present those qualities 

 which make it attractive to the e^'e. In its natural state it is often 

 opaque, dull, or flawed, and even if transparent and Hawless its form 

 is rarely adapted to the display of those characters which distinguish 

 the fashioned stone. Occasionally a gem stone may, without artificial 

 treatment, show to a sufficient degree those qualities which give it 

 rank; but such cases are rare, and in order that its inherent beauty 

 may be developed to the maxinuun it should be cut and polished. 



The several styles of cut may all be brought under one or the other 

 of the following heads: I. Those bounded by plane surfaces only. II. 

 Those bounded by curved surfaces only. III. Those bounded ])y l)oth 

 curved and plane surfaces. The several examples under the above 

 heads may be tabulated thus: 



I. Bounded by plane surfaces: 

 Brilliant cut. 



Double brilliant or Lisbon cut. 

 Half brilliant or single cut. 

 Trap or split brilliant cut. 

 Portuguese cut. 

 Star cut. 



Rose cut, or briolette. 

 Step brilliant or mixed cut. 

 Ta))le cut. 

 II. Bounded by curs-ed surfaces: 

 Double cabochon cut. 

 Single cabochon cut. 

 Hollow cabochon cut. 

 III. Bounded by curved and plane surfaces — mixed caljochon cut. 



BRILLIANT CUT. 



The brilliant cut may be described as two truncated pyramids, placed 

 base to base. The upper pyramid is called the crown^ and is so trun- 

 cated as to give a large plane surface; the lower one, called tho. jxiull- 

 ion, terminates almost in a point. The line of union of the two 

 pyramids is called the {lirdlc, and is the widest part of the stone. This 

 fashion of cut, though occasionally modified as to the size, mutual pro- 

 portions, and even the number of facets, lequires, when perfect, 58 

 facets. The uppermost facet is called the crown., and is formed by 

 removing one-third of the thickness of the fundamental octahedron; 

 the lowermost facet is called the ciilet., or collet^ and is formed by 

 removing one-eighteenth of the thickness of the stone {a and ?>, in 

 text fig. 14). The triangular facets touching the table (s in c, fig. 14) 

 are called star facets; those touching the girdle fall into two groups, 



