Becker — Auriferous Conglomerate of the Transvaal. 193 



Art. XXYII. — Auriferous Conglomerate of the Transvaal ;* 

 by George F. Becker. 



The auriferous conglomerate of the Witwatersrand gold- 

 field, South African Republic, constitutes the most important 

 gold deposit ever known. Without counting imperfectly 

 explored extensions, the workable area is a strip of country a 

 couple of miles in width and about 30 miles in length. This 

 little district has yielded since 1887 about 240 million dollars 

 worth of gold, and careful estimates indicate that only 

 about one-fifteenth of the accessible gold has been extracted. 

 The production is increasing rapidly. The output in 1897 was 

 one-third greater than that in 1896, and reached 3,034,674 

 ounces, worth about $51,675,550. During 1897 the other gold 

 fields of the Transvaal (which equals Arizona in area) produced 

 enough to bring the total product up to $58,434,000. The 

 total product of the United States in 1896 was in round num- 

 bers 53 million dollars, but that for 1897 is estimated at 61 J 

 millions. f It is evident that the banket is a very notable 

 factor in the financial policy of all commercial nations, and 

 even in the party politics of the United States. 



The nature of this wonderful deposit is a subject of mani- 

 fest interest to geologists and mining engineers, who, however, 

 have arrived at various conclusions. No considerable doubt 

 exists that the puddingstone is a marine littoral deposit, but 

 some observers have held that the gold is detrital, being part 

 and parcel of the conglomerate ; others that it is a chemical 

 precipitate from the ocean in which the pebbly beds were laid 

 down ; and still others that the precious metal reached the 

 uplifted but uncemented gravel in solution, so that the ore- 

 bearing strata are allied to ordinary veins. Two authorities 

 regard the deposits as in part detrital and in part venous 

 impregnations. 



The banket skirts the southerly edge of a large area dotted 

 over with proclaimed gold-fields in which ordinary veins are 

 associated for the most part with crystalline schists. This area 



* This paper, which has been prepared at the request of the editor of this 

 Journal, is essentially an abstract of a longer one, "The Witwatersrand Banket 

 with notes on other Gold-Bean ng Puddingstones," U. S. Geol. Survey, Ann. Rep., 

 1896-97, Part V It contains, however, references to opinions by Messrs. 

 Stelzner and Zirkel, which I had overlooked ; and to a paper by Mr. John Hays 

 Hammond which has just appeared. For permission to publish this material T am 

 obliged to Mr. R. H. Benson. 



f The South African mining companies turn in statistics of their production 

 with admirable promptitude, but unfortunately in terms of ounces of crude bullion 

 and in spot values. The returns of the Knglish mint show that the average fine- 

 ness is - 8475 or $17.52 per ounce, coining value. 



Am. Jour. Sci. — Fourth Series, Yol. V, No. 27. — March, 1898. 

 13 



