EMIGRANT DIAMONDS IN AMERICA.'^ 



By Prof. William Herbert Hobbs. 



To discover tho origin of the diamond in nature we must seek it in 

 its ancestral home, where the rocky matrix gave it birth in the form 

 characteristic of its species. In prosecuting our search we should very 

 soon discover that, in common with other gem minei'als, the diamond 

 has been a great wanderer, for it is usually found far from its original 

 home. The disintegrating forces of the atmosphere, by acting upon the 

 rocky material in which the stones were iml)edded, haveloosed them from 

 their natural setting, to be caught up by the streams, sorted from their 

 disintegrated matrix, and transported far from the parent rock, to be 

 at last set down upon some gravell}^ bed over which the force of the 

 current is weakened. The mines of Brazil and the Urals, of India, 

 Borneo, and the "river diggings'' of South Africa either have been 

 or are now in deposits of this character. 



The " dry diggings '' of theKimberl}" district, in South Africa, afi'ord 

 the unique locality in which the diamond has thus far been found in its 

 original hom(\ and all our knowledge of the genesis of the mineral has 

 been derived from study of this locality. The mines are located in 

 "pans," in which is found the "blue ground'' now recognized as the 

 disintegrated matrix of the diamond. These " pans" are known to be 

 the "pipes," 'or "necks," of former volcanoes, now deeply dissected 

 by the forces of the atmosphere — in fact, worn down if not to their 

 roots, at least to their stumps. These remnants of the "pipes," 

 through which the lava reached the surface, are surrounded in part ])y 

 a black shale containing a large percentage of carbon, and this is 

 believed to be the material out of which the diamonds have been formed. 

 What appear to be modified fragments of the black shale inclosed 

 within the "pipes" afford evidence that portions of the shale have 

 been broken from the parent beds by the force of the ascending current 

 of lava — a common enough accompaniment to volcanic action — and have 

 been profoundly altered by the high temperature and the extreme 

 hydrostatic pressure under which the mass must have been held. The 



"Reprinted from Popular Science Monthly, New York, Vol. LVI, Noveni1)er, 1899, 

 by permission of D. Appleton &Co., owners of copyright. 



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