140 SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



These relations will be further considered with the description of each special diaman- 

 tiferous deposit. 



The nature and character of the original mother-rock, in the debris of which the 

 diamond is now found, has nowhere been determined with the certainty and clearness as to 

 detail that is desired, although many important steps have been made towards the solution 

 of this important problem. In the following pages we will consider in detail the facts 

 connected with each well-established occurrence of diamond, and endeavour to determine 

 the origin of the stone in each case so far as the available observations permit. In any 

 case it is certain that the original mode of occurrence and the mother-rock are not the 

 same at all localities : in some cases the mother-rock is without doubt one of the older 

 crystalline rocks, such as a gneiss or a crystalline schist, or an eruptive rock, such as granite ; 

 in other cases it is highly probable that diamond originated as a secondary mineral in 

 ci-evices in the rock known as itacolumite, as will be specially considered when we come to 

 treat of the Brazilian deposits. In the South African diamond-fields, the stones are 

 found for the most part embedded in a green serpentine-like rock, instead of in loose 

 sands as is more usually the case. This mode of occurrence, which is peculiar to this 

 locality, and differs from that of all others, will be considered in detail under its appropriate 

 heading. 



The different diamantiferous deposits will be dealt with below in the following order: 



1. India. 6. North America. 



2. Bi-azil. 7. British Guiana. 



3. South Africa. 8. Urals. 



4). Borneo. 9. Lapland. 



5. Australia. 10. In meteorites. 



1. INDIA. 



Diamonds have been known longer in this country than in any other, and the most 

 beautiful, famous and many of the largest stones were found here. A diamond river in 

 India is referred to by Ptolemy ; and the fact that diamonds were known to, and highly 

 prized by, the ancient inhabitants of the country is proved by the rich adornment of the 

 oldest temples of religion with this and other precious stones. The sacred shrines and 

 idols show, moreover, that the art of diamond cutting has been long understood. Until 

 the discovery of the Brazilian deposits in 1728, the supply of the whole world was derived 

 almost entirely from the Indian sources, Borneo being at that time the only other known 

 locality. 



The occurrences of diamond in India are distributed over an extensive area of the 

 country. C. Ritter in his ErdTcunde von Asien (vol. iv., part 2, p. 343, 1836) collected 

 together the various scattered reports concerning the diamond localities, and was the first 

 to give a detailed and connected account. More recently (1881), Professor V. Ball has given 

 an exhaustive account, in which he has incorporated all the latest information, in the 

 official Manual of the Geology of India (Part III. pp. 1-50). 



That the occurrence of diamonds in India is almost entirely confined to the eastern 

 side of the Deccan plateau is to be gathered from the finds of the present day and from the 

 reports of earlier times. The southern boundary of the region in which diamonds have 

 been found is the river Penner in latitude 14° N. ; from this river the diamond localities 

 form a frequently interrupted line running northwards on the east side of the Deccan 

 plateau, crossing the Kistna, Godavari and Mahanadi rivers, and reaching the southern 



