72 [APPENDIX 



intrusion of igneous rocks with which the quartz is found in connection 

 has occurred during a comparatively recent period. 



As these rocks have forced -their way to the surface through all the 

 species that lie above them, they can be considered in no other light 

 than having an age posterior to most of the tertiary rocks within the 

 State, or the northern and middle parts of it; and Cotemporaneous. at 

 least with the lower portion of the' miocene period. Under these cir 

 cumstances it is not to be wondered at that gold may be found in San 

 Francisco or Contra Costa, as the geological formations which have de 

 veloped it east of the great rivers, are found also in the mountains to 

 the west, though not to the same extent. 



The disturbance >f the recent sedimentary rocks of the Coast Moun 

 tains, and the character of some of the intruded masses that has pro 

 duced the tilting and dislocations, their identity with the stratified rocks 

 on the eastern border of the great valleys, leads us to the conclusion 

 that the causes of uplift which have been found among the latter, --were 

 continued partially to the coast in the same period. With respect to the 

 agents that played, an important part in these turbulent periods, there 

 can be but little trouble in their discrimination, and ample testimony is 

 found to identify them with the recent group of igneous rocks under 

 consideration, and if these conclusions are correct, the character for per 

 manency of these viens is beyond all cavil or doubt. 



Future investigation may disprove this position, but until it. is made 

 evident that the veins of the recent group have been disturbed by other 

 and more recent vulcanic agents on either side of the g^reat rivers, we 

 can regard them in no- other view than being among the last of an ex 

 tensive series of disturbances which have operated principally through 

 a large portion of the west flank of the Sierra Nevada at a comparatively 

 recent period in the geological history of this part of the continent. 



The metalliferous character of this .group is in no way inferior to that 

 of the older ranges of these rocks; the proof of this rests in the fact, 

 that some of the best placers yet found in this country are included 

 within its boundaries among the alluvium and drift deposits of the ter 

 tiary epoch. The gold generally found in these placers is of that char 

 acter known among the miners as "rough or recent gold," having 

 suffered but little from attrition by water; but it is not unfrequent to 

 find the recent metal associated with that which has been much worn by 

 attrition, and the two qualities thus appearing in the same placer range, 

 can be regarded only as having different orri<rms and ages. It would 

 scarcely appear reasonable to suppose that two pieces of metal driven 

 from the same source and subjected to the same action, should present 

 smooth and rounded surface in the one, while its fellow beside it shall 

 retain all its angularities as though just detached from its original 

 matrix. 



With reference to the older group of these veins there are features 

 manifest which are both interesting and important, when we consider the 

 immediate position of the recent group, to those of the older where both 

 are found in contact. -It has been remarked in the preceding pages 

 that the veins of* the older series have disturbed the greenstone below 

 and the granite above only ; a casual examination of the district in 

 which these veins occur, would convey to the observer an idea that a 



