356 



2 AND THEORETICAL DISCUSSION, 





manifestations of volcanism, accompanied by ejections of lava, as, for in- 

 stance, along the greater portion of the Appalachian Chain, and especially 

 on its eastern border, no definite statement can be made in regard to the 

 geological period of the metalliferous impregnation. It would appear, 

 however, that the evidence is, on the whole, in favor of this having taken 

 place at the time of, or shortly after, the upheaval of the ranges themselves. 

 To prove that the rocks of such ranges as the Appalachian and Scandi- 

 navian, which are surrounded by entirely unaltered Cretaceous and Tertiary 

 strata, have been the scene of extensive chemical reactions during those 

 later periods would be a difficult task.* Under any circumstances, there is 



no basis for MurchisonY idea that gold was 



to use his own words 



u 



the 



last formed of the metals" ; for the impregnation of the quartz veins, or rather 

 its segregation, at the same time with the quartz, into veins or vein-like 

 masses, was merely a collecting together of particles previously existing in 

 the rock, and not by any means a new creation of them. 



On the purely chemical question, by the aid of what solvent the golden 

 particles were carried into the position which they occupy, or have once 

 occupied, in the veins, no light seems thus far to have been thrown by the 

 investigators who, in various parts of the world, have occupied themselves 

 with this problem. That the gold and the quartz were introduced into the 

 vein-fissures or segregated into vein-like masses contemporaneously with each 

 other, would seem, from the manner in which the two substances occur 

 together, to be beyond doubt. Why they thus occur, or why this metal is 

 so rarely found in any other gangue, — as, for instance, calcite, — is a question 

 which cannot yet be answered. Neither has any chemist been able to advance 

 the first step toward an explanation of the fact that native gold never occurs 

 otherwise than as an alloy with native silver. 



Some other problems have ensmo;ecl the attention of those who have made 



o^o 



a, s 



special study of the chemistry and mineralogy of gold regions. One of 

 these is the apparently commoner occurrence of nuggets f of large size in the 



* The most extraordinary of Murchison's theories is that held by him in regard to the relative value of 

 silver and gold, which he thus sets forth in the last edition of "Siluria" (p. 475) : " Before quitting this 

 theme, I would simply say, as a geologist, that Providence seems to have adjusted the relative value of these 

 two precious metals for the use of man, and that their relations, having remained the same for ages, will 

 long survive all theories." One knows not which to wonder at most,, the idea here expressed, or the fact 

 that it is put forth as a geological statement. 



t "Nugget" seems now to be the most generally accepted term for a "sizable" rounded piece of native gold. 

 It appears to be a word of Australian origin, and is the equivalent of the Spanish "pepita" (seed, pip ; pepUe 

 in French) or "chispa" (a spark or brilliant). "Scad" is the. American for nugget, but, so far as the writer 

 knows, of recent origin, and not in general use, even among the miners. 



