DIAMONDS AND PEARLS 





OEM-STONES 



MAJOR 



Pearls 



part of th Peninsula. The southern of (ho throe group* of diamond 



in. hides local it les, with apparently audic-ntic rci-.,rds, in the d, 



liellary, Karnul. K. tn.i. and ( iodavari. Looso stones have been picked up 



on the - ui lace of the Around, found in deposits of alluvium and in the workings 



winch have boon underiaki-n in i he to called Banaganpilly stage of ti.. 



Maries of strata. In the -up of occurrences, in tho Slahanadi -..ill. .. :> . >: 



a\e he, -ii found ill tin- alluvium ol the San 1 1 lal | M ir and ('hand.: 

 mil though strata similar to those of t In- Vindhyans and Karnul* are 

 known in this area, no diamonds have boon found in thdttt older rook*. The third 

 j/r.'Up of occurrences occupies a tract some sixty miles long by (en mil.--, wide. 

 \\nli the \indhyan conglomerates near Panna as the centre. Tim diamond 

 industry still persists in this area, both in the old conglomerate of \ m 

 Ihyan .1. -. and in deposits which, though described as alluvium, are, possibly 

 relic-i of l.ameta (Upper Cretaceous) deposits." 



Tho diamond, on account of its hardness, has for long been made use of 

 for elan-cutting purposes. A rude variety, known as Bort, hns been chieily 

 employed in this way. In medicine, diamond dust is known to be a powerful 



uical poison. [Gf. Hedges, Diary, 1681-7, iii., cxxv., etneq.; Heyne, Tracts Mechanical 

 Ind., 1814, 92-107; Bornior, Trnn-lx, llir>fi us. app., 469-71 ; King, Ind. Ayri.. 

 o\ . 1892 ; Madras Weekly Mail, Dec. 13, 1900, 562 ; The Pitt Diamond, confer 

 alter Fitz-Patrick, Kept. Hist. MSS. Comm., 1892 ; Brough, Mining of Non- 

 etall. Min., in Journ. Soc. Arts, Jan. 15, 1904, 168-72.] 



r.u.i. i. 



ImliistrUl UM>. 



all 



I 



3. Pearls, Pearl Fisheries and Mother-of-pearl. Pearls 

 found in several mollusrs which inhabit shallow seas and sandbanks 

 both the Old and New Worlds. The most productive is the so- 

 ed " Pearl Oyster," in realitya mussel M*'/<'<i</rinn nnn-(/ 

 Modern classification, however, favours its reduction to 

 i, in nit i, muthu, etc. 



Formation. It is now known that most pearls are formed by the presence 

 of some foreign substance, which becomes embedded in the interstices of the 

 molluscan mantle and constitutes a source of irritation. This irritation causes 

 (ho mollusc to deposit nacreous matter in concentric layers until the foreign 

 particle becomes completely encysted. It has been practically established, 

 chiefly through the investigations of Dr. Lyster Jameson, that the irritating 

 substance which induces the pearl -formation is very seldom a sand grain, but 

 almost always a small parasite, in some cases a simple protozoan, in others one 

 the stages in the life history of a flat worm. Prof. Herdman of Liverpool, 

 ho was requested to examine the fisheries in the Gulf of Manar, states in his 

 report that the majority of the best pearls contained as their nuclei the remains 

 of certain Platyhelminthian parasites, which he identified as the larval con- 

 dition of a Cestode or tape-worm. This cestode passes from the body of the 

 pearl oyster into that of a file-fish and from the file-fish into some larger animal, 

 iQssibly the large Trygon or ray. 



Though pearls originate in the mantle, they nevertheless, when large, fre- 

 uently work their way out and lie loose between it and the shell, or become 

 attached by subsequent nacreous deposit to the " mother-of-pearl " surface of 

 the latter. In this position a pearl may become so covered up as to form a 

 hemispherical mass which when cut out forms the " perle bouton " of the jewel- 

 lers. The hollow warty pearl, known as " blister pearl," is produced by a 

 deposit of nacre in order to close an aperture arising from some injury. 



Indian Fisheries. The pearl fisheries of India have been famous from remote 

 times. Garcia de Orta in 1563 (Coll., xxxv.) mentions the principal localities 

 in the Persian Gulf where pearls were then obtained and says the pearls were 

 cleaned and polished with pounded rice and salt. Linschoten in 1598 and 

 Ta vernier in 1676 describe both the Persian and the Ceylon pearl fisheries. At 

 the present time the largest pearl fisheries in the East are those of Ceylon, 

 for information concerning which the reader should consult the reports sub- 

 mitted to the Government of Ceylon in 1904 by Prof. Herdman, Mr. J. P. Lewis 

 and Mr. Hornell ; also Herdman's much fuller report published by the Royal 

 Society (London, 1903-6, 5 vols.). In 1905 the total amount realised was 

 Rs. 25,10,621, and the number of oysters fished up 49,250,189. These fisheries 

 (it is understood) have been recently sold, or rather leased, for 20,000 a year 

 to a company who are to work them. The only other pearl fishery of importance 



557 



D.E.P., 

 vi., pt. i., 

 117-22. 

 Pearls. 



Parasitic 

 Action. 



Formation. 



Blister Pearls. 



Fisheries. 



Ceylon. 

 Upturns. 



