146 



BULLETIN 118, UNITED STATES NATIONAL MUSEUM. 



with a smaller curvature on the base than on the crown. The 

 single cabochon is a characteristic cut for the turquoise. The hollow 

 cabochon is adapted to very deep-colored transparent stones. The 



Fig. 26.— The cabochon cut. a, the single cabochon; b, the double cabochon; c, the hollow 

 cabochon; d, flat or tallow top cabochon; e, mixed cabochon. 



mixed cabochon has either the edge or side faceted, or both. In all 

 of the cabochon cuts the arches may be of a varying degree of flat- 

 ness, depending upon the nature of the stone. 



CAMEO AND INTAGLIO. 



The term "cameo" is applied to any engraving in relief upon the 

 surface of a gem, usually upon a stone like onyx or a shell composed 

 of layers of different colors, the engraving being of sufficient depth 

 to expose the underlying layers and producing the desired contrast. 

 An intaglio differs in being an incised engraving and usually upon a 

 stone of uniform color throughout. 



