CHAPTER XIX. 

 THE LUSTER OF THE PEARL ITS CAUSE EXPLAINED. 



SINCE the earliest records of the pearls's history, 

 its magic charm has won the admiration of the 

 people of nearly every land. The earliest rulers 

 and conquerers were captivated by its tender, silky luster 

 and from their time to the present, pearls have been the 

 most important gems of royalty. Their great popularity, 

 lasting over 2,400 years, is the very strongest recommen- 

 dation for the pearl. These beautiful gems have several 

 attributes which make them valuable, but the one virtue 

 which charms and wins the people of all times is their 

 soft, velvety luster. While this remarkable silky sheen 

 is so greatly admired, the cause of the unusual appear- 

 ance is not immediately obvious. Fine pearls and the 

 portions of the shells in which they are found have this 

 Oriental radiance. The shells consist of thin layers of 

 carbonate of lime, interstratified with animal membrane. 

 The various layers of nacre follow the form of the shell 

 and are slightly inclined toward the surface. This pecu- 

 liar structure of the laminae is easily discerned in the pos- 

 terior adductor scar of the shell, where the edges of the 

 strata slightly overlap each other. The tender, delicate 

 irridescence can be plainly seen, yet a microscope reveals 

 the full glory of the wonderful creation, where the ar- 



173 



