1857.1 Western North Carolina. 55 



The question very naturally arises, how has this condition of 

 things been produced ? 



Says one : " It is quite evident that the whole vein up to the very 

 surfiice (and far into the air, for it has suffered from the same de- 

 nudation that has molded the surrounding country,) was originally 

 a compound sulphuret of iron and copper. The rains on the hills 

 finding their way down from the surface through the upper part of 

 the vein, and issuing in springs at water level, and having gradu- 

 ally filtered down the copper to water level, and carried off the sul- 

 phur, leaving all the upper mass a red oxyd of iron, and underneath 

 it a transverse layer of precipitated black oxyd of copper, below 

 which, the process, of course, could not be carried on, and the vein 

 remains a body of sulphuret of iron and copper."* 



Another says : " The vein was once undoubtedly filled to the top 

 with this material. (The sulphuret of iron and copper.) The gos- 

 san and the black oxyd have been derived from its decomposition, 

 which has taken place mainly, as we think, through the action of 

 water. The original 'arsenical' ore, in the slow progress of its de- 

 composition downwards, has left behind the resulting light porous 

 gossan. The heavier black oxyd, on the other hand, in some form 

 or other, has been constantly carried downwards, until it has formed, 

 resting immediately on the undecomposed mass, the bed of black 

 ore as we now find it." 



Among the specimens in the writer's possession, there are some 

 of the yellow copper ore, in which the ' arsenical iron ' is the ex- 

 clusive gangue stone ;f in others there are crystals of tremolite, 

 or other earthy minerals allied to hornblende, disseminated through 

 the arsenical iron, side by side with the yellow copper ore ; while in 

 others still, the arsenical iron is absent, and these earthy minerals, 

 alone, compose the gangue stone. Now, wherever a copper vein has 

 but little or none of the arsenical iron associated with its ores, there 

 the explorer for copper leads must expect but little or none of the 

 iron gossan on the surface, because there has been nothing in the 

 vein from which it could be formed. In such cases, the lead must 

 be traced by other indications, well known to Geologists 



Another remark is needed, in reference to the origin of larger or 



* Report of J. B. Lesley, Esq., Topograpliical Geologist. 



fThe term pangue rock is applied to any rock, or oue wliich includes in its mass any- 

 valuable metals. 



