446 TRANSACTIONS OF THE 



found in drift and alluvial deposits. This was disproved some forty years 

 ago, by a M'Barringer of North Carolina. Gold being found on the banks 

 of a stream on his plantation, he remarked, 1st. that it was renewed after 

 being exhausted ; 2nd, that none was found abovp a point in a gully which 

 the stream had cut through a hill. He therfore sought the source of the 

 gold on the banks of the gully and discovered a vein of white sulphate of 

 baryta containing nodules of gold. Since that time the idea of auriferous 

 veins has become familiar in geology. In the gold regions of North Car- 

 olina, the superficial soil is most frequently a white or red clay. The 

 speaker stated that he came to the conclusion, that the former was derived 

 from the decomposition of a granitoid or gneiss rock, the latter from that 

 of a greenstone. On the surface of the fields, were to be seen what were 

 locally called pointers, generally angular masses of quartz, indicating the 

 course of the veins, of which they had been portions. Although veins were 

 frequent and easily discovered, it did not appear that the working of them 

 had been generally successful in North Carolina. 



The mine in which he was concerned, yielded a pyritical ore. By ana- 

 lysis, it appeared to contain from twenty-five to forty dwts. per bushel, 

 weighing about 112 lbs. This is considered lich for an auriferous vein. 

 The actual products, however, did not amount to more than one-third of 

 the analysis. He came to the conclusion that the gold was not merely 

 disseminated through the iron pyrites, but was mineralized, so that the 

 ore was a double sulphuret of iron and gold. 



The gold not obtained by the first process, was to be obtained in 

 part by a subsequent operation, after exposure to the air. In this way he 

 had been informed that more gold had been obtained from the mass of 

 waste than was yielded originally. 



The quantity of gold found in a given weight of vein rock, is as a gen- 

 eral rule, less than that found in drift or alluvium. For this fact, there is 

 an obvious and simple mechanical reason. When veins are disintegrated 

 by the action of water, the lightest poi'tions are carried to the greatest dis- 

 tances ; thus the earthy matter is removed and the gold left in greater 

 relative quantity. Thus, washings may be rich, while the veins whence 

 they derive their origin are not worth working. It has been said that 

 quartz veins are profitably worked in California, but this has not been the 

 ease in North Carolina or Virginia. 



The Chairman stated, that this idea of veins being profitably worked in 

 California, had not only been doubted but formally contradicted. 



Prof. Renwiek went on to state that no earthy matter or vein rock 

 had ever yielded in practice the whole of the gold contained it it. Even 

 when carefully washed by hand, a gentleman engaged in mining in the Col- 

 umbian province of Antiguera, had never obtained more than 50 per cent, 

 of the gold, and thought that to get from 25 to 30 per cent, by machinery, 

 was a great success. 



The pyritical ores are difficult and costly to work. By long exposure to 

 the air the sulphuret of iron may be completely decomposed, but the space 



