116 THE WEALTH OF THE SEA 



Detection of Imitation Pearls 



Although the uninitiated cannot distinguish real 

 pearls from the imitations, a jeweler or any other 

 person familiar with pearls can do so at a glance. 

 The genuine pearl is 2.6 times as heavy as water, is 

 opaque, and is not affected by acetone or amyl ace- 

 tate, but is readily attacked by strong acids. The 

 hole in a genuine pearl is drilled and therefore does 

 not resemble a hole in a glass bead. The surface of 

 true pearls is somewhat iridescent, giving a faint 

 play of colors, and does not give a well defined reflec- 

 tion; it can be scratched by a sharp knife. 



Since the hollow glass bead imitations are glass 

 outside, they give sharp, well defined reflections, and 

 cannot be scratched except with the substances that 

 will cut glass. They are usually light; the wax-filled 

 ones often float on water. The surface is not attacked 

 by any acid except hydrofluoric. 



The "indestructible" imitation pearls are lac- 

 quered opalescent glass beads; for this reason they 

 are usually translucent and appear yellowish when 

 held before a light. They owe their luster to their 

 coating of pearl essence lacquer, which can be cut 

 or peeled off or dissolved off with amyl acetate or 

 acetone. This coating is inflammable and seldom 

 extends smoothly up to the very edge of the hole. 

 To distinguish between an imitation of this type and 

 a genuine pearl, the two are immersed in acetone ; the 

 true pearl will not be affected, but the coating of 

 the imitation will be dissolved. 



