ats and one in the South Kensington 

 Museum weighs 455 carats. The small- 

 Pearls used in jewelry are known as 

 seed, dust or sand Pearls. 



Pearls are chiefly white in color, but 

 many are tinted yellow or pink ; some 

 are grey, green or purple and many other 

 colors occur. Black Pearls are obtained 

 in certain fisheries. The Pearls from the 

 Unios of North America are of almost 

 every shade. 



Pearls of pure white color, if of the 

 proper luster, ar-e those most highly 

 prized in Europe and America, although 

 a slight pinkish tinge does not injure 

 the value. They must, however, have 

 the transparency of the true Pearl and 

 not be "chalky." 



In China and India, Pearls of yellow 

 color are preferred. 



The hardness of Pearl is 4 and its spe- 

 cific gravity 2.65-2.68. It is thus like 

 that of shell or "mother of Pearl," which 

 might be expected from the fact that 

 both are of the same chemical composi- 

 tion — carbonate of lime. Owing to 

 their low hardness Pearls are easily 

 scratched and on account of their com- 

 position are attacked by acids. They 

 thus deteriorate with age, losing their 

 polish and luster and often becoming 

 black and unsightly. No way of restor- 

 ing the luster of Pearls is known, al- 

 though occasionally the outer marred 

 coating can be removed by those skilled 

 in the art and an equally lustrous sur- 

 face be found beneath. To preserve 

 Pearls as long as possible they should 

 be wiped with a clean linen cloth each 

 time after being worn, and be kept in a 

 dust-tight box, carefully wrapped in 

 linen. Hot or boiling water injures and 

 in time destroys their luster, and many 

 valuable Pearls have been ruined because 

 the mollusk which contained them was 

 boiled before opening. 



The moUusks which yield Pearls are 

 many, and Pearl fishing is an industry 

 carried on in many parts of the globe. ^ 



The Pearl mollusk or Pearl oyster, 

 par excellence, is that known by the 

 scientific name of Meleagrina (Avicula) 

 margaritifera. This mollusk has a 

 bivalve shell averaging seven or eight 

 inches in diameter and generally thick. 

 The exterior is of a greenish black 

 color, while the interior is silver white 



with pearly luster. The latter forms 

 indeed the well-known "mother of 

 Pearl." This mollusk inhabits warm 

 seas, occurring especially in sheltered lo- 

 calities in the Indian Ocean and occa- 

 sionally throughout the tropical zone of 

 the Pacific Ocean. It groups itself in 

 colonies like the common oyster, usually 

 on coral banks, at a depth of twenty to 

 thirty feet. It is not free moving, but 

 attached by a byssus, which must be sev- 

 ered before the mollusk can be brought 

 to the surface. The Pearl fisheries of the 

 Indian Ocean chiefly center in the 

 Straits of Manaar between India and 

 Ceylon. The fishing is largely confined 

 to the months of March and April, as 

 the sea favors best at that time, and at 

 that season from 15,000 to 20,000 fishers 

 and dealers are said to gather along the 

 Pearl Coasts. The oysters are obtained 

 by divers, who go out in boats and se- 

 cure the shells by diving. They usually 

 dive without appliances and work under 

 the water simply by holding their breath 

 for the time. Some fishers, however, 

 make use of diving suits and bells. The 

 work is dangerous, not only on account 

 of the bodily strain, but because sharks 

 prey upon the divers. The oysters are 

 unloaded from the boats into pits on the 

 shore, where they are left to putrefy, 

 and the Pearls are then washed out. 



Other localities in the Orient where 

 the Pearl oyster occurs and where Pearl 

 fishing is carried on in the same man- 

 ner as above described are the Persian 

 Gulf, the Red Sea and the Sulu Archi- 

 pelago'. The Red Sea fisheries furnished 

 in earlier times an extensive supply of 

 Pearls and were probably the source of 

 those used by the Romans. They are 

 now, however, largely exhausted. The 

 Persian Gulf Pearls are inferior in color 

 to those of Ceylon and are known as 

 "Bombay" Pearls. The Ceylon fisheries 

 are under control of the colonial govern- 

 ment and are carefully guarded to pre- 

 vent exhaustion of the supply. The lo- 

 calities where the fishers are to work 

 are staked off and when an area has once 

 been worked over it is allowed to lie "fal- 

 low" for seven years, so as to allow a 

 new crop to grow. 



So far as the American continent is 

 concerned, the true Pearl oyster is found 

 chiefly in the Gulf of California. It oc- 



41 



