CHAPTER 7 



Pearls and the Pearl Industry 



By A. E. Alexander 



Assistant Treasurer, Tiffany ir Co., New York 



The Nature of Genuine Pearls 



Natural or genuine pearls, composed mostly of calcium carbonate and held 

 together by a tenuous network of organic matter known as conchiolin, are formed 

 when some foreign substance is accidentally ingested into the shell of a pearl- 

 bearing moUusk. The irritant may be a grain of sand, a particle of silt, or a 

 parasitic form of life, such as a trematode. If there is no evidence of an irritant, 

 scientists believe the causative agent to be of wholly organic and internal origin. 

 Shortly after the deposition of pearl substance decomposition of the organic mat- 

 ter ensues, the final product revealing nothing of what initiated the process. 



The pearl oyster unable to rid itself of the unwelcome intruder seeks to reduce 

 the attendant irritation by coating the substance with a nacreous material. Once 

 the formation of calcium carbonate has started, the microscopic pearl itself be- 

 comes the irritant. The process continues until the organism dies, the pearl is 

 self-ejected, or the mollusk is brought to the surface by man. 



A natural pearl, examined under a microscope, structurally resembles an onion 

 in that numerous layers of extreme thinness are concentrically deposited from the 

 innermost to the outermost part of the jewel. The iridescence of a fine pearl can 

 be attributed to the incident light that is reflected and refracted from the surface 

 of its translucent layers. 



Pearls have four general shapes: spherical, button and ovoid, pear, and baroque, 

 or badly misshapen. The origin of all the types may well result from any one of 

 the several causes mentioned. These pearls may be foiTned in different parts of 

 a pearl-oyster's musculature system. Occasionally, the pearl may form as part 

 of the shell; such a pearl is referred to as a "blister pearl." 



The finest salt-water pearls are called "oriental pearls" in the trade. The term 

 "oriental," however, should properly be confined to pearls found in the Persian 

 Gulf or those obtained from the waters of Ceylon, and should not include all 

 pearls found in salt water. 



Salt-water pearls are formed in shells that have the generic name of Margariti- 

 fera. There are several species in the genera, ranging from a small shell the size of 

 a man's hand, as those obtained from the Persian Gulf (M. milgaris), to one 

 measuring up to 15 inches across (M. maxima), found in the coastal waters off 

 northern Australia. 



Natural pearls occur in a wide variety of colors: rose, cream, white gray, 

 bronze, black, shades of lavender, blue, yellow, orange, brown, and green. Black 



107 



