416 QUICKSILVER DEPOSITS OF THE TACIFIC SLOPE. 



CONCLUSIONS. 



Conclusion as to character oi deposits. — The maiiy analogies of tliG various ore 

 deposits thus point to a common origin of the ores, viz, precipitation in fis- 

 sm-es from ascending- hot solutions. In the following- chapters it will also 

 be shov.n that the derivation of the ores is inexplicalde except upon the sup- 

 position that the solutions ascended in a heated state. Portions of many of 

 the deposits can only be described by themselves as simple fissure veins, 

 and the existence of fissures is evident in all of them. The prevailing type 

 of deposit in the deeper mines is the chandjered vein, where the chandjers 

 are sometimes reticulated masses and sometimes impregnations. The ore 

 often follows the bedding for a certain distance and such portions of the 

 deposits are bedded veins. 



Cap cluunbers are frequent and in many cases contain most of the ore. 

 Stockworks without a known immediate connection with chambered veins 

 have been met In some mines, but these are probably in every case cham- 

 bered branches of veins. Of all the principal types of ore deposits, substi- 

 tuted masses alone seem to be absent. The quicksilver deposits of the 

 Coast Ranges ai-e on the whole more irregular than the deposits of average 

 ores in other regions. Tills is due to the heterogeneity of the rocks in which 

 they occur; but irregularities of precisely the same kind are found in veins 

 of other metallic ores the world over and no fundamental distinction exists 

 between deposits of cinnabar and deposits of other metals. 



Age of inclosing rocks. — The greater number of the productive mines have ex- 

 tracted their ore from chambers in rocks of Neocomlan age. This fact does 

 not seem to be due to any precipitating influence of these rocks, which, when 

 unaltered, are of exactly the same composition as the Tertiary beds. Still 

 less does the association indicate great antiquity for the deposits. The main 

 lines of disturbance in California, as elsewhere, are marked by ranges, and 

 these are for the most part considerably eroded. In consequence, the older 

 strata, where they have once been covered by rost-Neocomian rocks, have 

 been re-exposed along the old axes of compression. Kenewed movements 

 always tend to follow the old lines, and thus the fissures and ore deposits, 

 though of comparatively very recent date, are found most abundantly in the 

 earliest sedimentar}^ rocks of the region. Tlie physical character of the rock 



