196 THE GENESIS OF THE DIAMOND. 



So much, it may be claimed, is known about the physical properties 

 of the diamond, but how the diamond has been formed or crystallized 

 is a question still debated by scientists. 



Upon the information at hand it may be assumed that all diamonds 

 found prior to the discovery of the Kimberley pipes or craters came 

 from alluvial deposits and had been waslied down by the disintegra- 

 tion of the original matrix. Such was the character of the formation 

 in which the noted diamonds of India were found, which is described 

 as a layer of broken sandstone, (|uartz, jasper, flint, and granite, 

 interspersed with masses of calcareous conglomerate, the whole being 

 about 20 feet thick and covered with a few feet of black " cotton soil." 

 Here were the great mines of Gani-Coulour and Gani-Parteal, whence 

 came the Koh-i-nur (793 carats), the Great Mogul (787.5 carats), 

 the Regent (410 carats), and many other historical stones." 



The India mines were noted nuire for the size and purity than for 

 the quantity of the gems they jjroduced. There had been no consider- 

 able production of diamonds outside of the Deccan fields until the 

 discovery of diamonds in Brazil in the year 1728. Here, in the 

 province of Minas Geraes, rich beds were opened in an alluvial 

 deposit of clay, quartz pebbles, and sand, charged with iron oxide.'' 

 In many places the diamond-bearing strata were buried under 30 

 feet or more of alluvial detritus. These deposits occurred along the 

 rivers, up the ravines to the ridges and plateaus, where conglomerate 

 beds were reached from which the deposits in the rivers had been 

 washed. The conglomerate Avas chiefly itacolumite, a micaceous 

 sandstone. The sandstone, being a fragmental sedimentary rock, 

 was not the original matrix of the diamond. Probably when the 

 sandstone was being formed the diamonds were washed down with 

 the detritus and became embedded in it. 



Diamonds have also been found in alluvial deposits in Borneo; 

 New South Wales; British Guiana; in the gold deposits of the Ural 

 Mountains, Australia, and California ; along the Vaal River in South 

 Africa ; and in many other localities. 



Before the discovery of the mines at Jagersfontein and Kimberley, 

 which occurred between August, 1870, and July, 1871, there is no 

 record that diamonds had been discovered in volcanic pipes or craters, 

 their occurrence having always been in alluvial or sedimentary 

 deposits. 



A few years ago diamonds were found in the battery mortar of a 

 mill at Klerksdorp in the Transvaal which was crushing gold ore 



« Voyages en Turqnie, en Perse et aux Indes, Tavernier, Paris, 167G. 



6 The Diamond Fields of Brazil, Pveport of United States Minister Bryan, 

 1899, conveying report of Secretary of Legation Dawson. A Treatise on Gems, 

 Lewis Feucbtwanger, M. D., 1867. An Account of Diamonds Found in Brazil, 

 James Castro de Sarmento. Travels in South America, J. J. von Tschudi. 



