' 









■ 





j*r**"»-*-™* 



360 



KESUME AND THEORETICAL DISCUSSION. 





With regard to the manner in which the gold in the quartz loses its char- 

 acteristic forms, so as to become transformed into the smooth rounded masses 

 occasionally found in the placer mines, there seems to be no theoretical 

 difficulty. In the first place, however, it may be stated that by no means 

 all the nuggets have this character. Many of them exhibit more of their 

 original character than would be expected to be found remaining after ages 

 of pounding between the boulders of the gravel. This is particularly true of 

 specimens collected by Professor Pettee from the hydraulic mines during his 

 last year's investigations, and which have been been carefully examined 

 by Mr. Wadsworth and the present writer. The same fact has also been 

 stated by Mr. Ulrich — who appears to be a close observer — in regard to 

 the Australian nuggets* There seems to be no doubt that a scraggy — 

 to use a common miner's term — piece of gold can be transformed into a 

 rounded smooth nugget by a sufficient amount of the right kind of rubbing 

 and hammering, which must have taken place as these great piles of detritus 

 were being shifted from place to place by currents of water. Some of the 

 specimens collected exhibit in the most interesting and convincing manner 

 the transitional form between the rough crystalline form and the smooth 

 rounded one. One in particular, from an unknown locality, purchased 

 by the writer in a shop at San Francisco, has one side almost perfectly 

 smooth, and rounded edges turned over upon the back, which itself is 

 covered with crystalline branchings, still retaining a large part of their 

 original delicacy. It is evident, in this case, that the specimen has been 

 protected on one side, while the other has been subjected to abrasion and 

 pounding, the result being a nugget, presenting at the same time and in 

 most remarkable perfection, the characteristic forms of quartz gold and 

 placer gold. 



That the masses of gold, when they have been released from the quartz 

 veins and have begun to be rolled about in the gravel, could by any possi- 

 bility be so situated as to become subjected to any chemical influences by 



— highly 





which their mass could be enlarged, seems — to the writer, at least 

 improbable. That occasionally pieces of the metal may be united by pres- 

 sure or by hammering between the gravel boulders, and that thus a larger 

 mass may be formed by the union of two or more smaller ones, through 

 purely mechanical agencies, seems not impossible ; and some observations 

 of Mr. Wadsworth appear to corroborate this view. 



* See R. Brough Smyth's " Gold Fields and Mineral Districts of Victoria " (18G9), p. 360 



