PEARLS AND THE PEARL INDUSTRY 



115 



clever propaganda, disseminated since World War I, the Japanese have led many 

 prospective buyers to believe that cultured pearls and genuine pearls are one and 

 the same thing. They claimed that only a "tiny irritant" is used to initiate the 

 process. Scientific tests, based on the sectioning, thin-sectioning, and X-raying 

 (radiography) of thousands of pearls of Japanese origin, have shown that these 

 pearls contain mother-of-pearl beads that measure from 75 per cent to 90 per 

 cent of the total diameter. The average thickness of nacre (pearl substance de- 



FiG. 7-3. Inserting mother- 

 of-pead bead in pearl oyster. 



{Photo by Robt. O. Smith) 



Fig. 7-4. Pearl oysters in 

 cages in which they are held 

 at a depth of about 35 feet 

 until the "cultured" pearls 

 develop. 



(Photo by Robt. O. Smith) 



