SIMILARITY OF THE DEPOSITS. 401 



structure so common in serpentine and from finalogy with tlie Servian ores. 

 The net structure in the California ores, however, is ratlier an evidence that 

 it did not replace serpentine, because neither at New Alniaden nor elsewhere 

 in the Coast Ranges has the net structure been found in the serpentine.^ 



SIMILARITY OF THE DEPOSITS. 



All the deposits similarly formed. — Everything sccms to polut to tlic liypotlicsis 

 that all the quicksilver ores of the Pacific slope have been formed in a 

 similar manner. The gangue minerals and their association are not identi- 

 cal at all the mines, but it will be found that the pecuharities offset one 

 another. It is quite true that quicksilver ores the world over are strikingly 

 similar in composition. The same minerals which are found abundantly 

 with cinnabar in California jire those most usually associated with it else- 

 where. Though other minerals, such as sulphides of lead and copper, are 

 also found with cinnabar both on the Pacific slope and in European mines, 

 they are rare. These facts do not weaken tlie evidence given by this 

 characteristic association of minerals that the deposits of the Pacific slope 

 have all been formed in the same manner, but rather tend to siiow ttiat 

 conditions accompanying the genesis of European deposits wert; siuidar to 

 those which attended the formation of the quicksilver ores of Aa erica. 



Comparison of the various localities described in former chapters 

 shows that a substantially complete series of transitions exists from de- 

 posits now forming to those in which there is every reason to suppose ore 

 formation ceased long since. This is true both as to the metliod of genesis 

 indicated and as to the form of the deposits; but it will be convenient to 

 deal first witli the former and then with the latter of these topics. 



Evidence as to method of genesis. — Thcrc cau, of coursc, bc uo possible doubt 

 as to the manner in which the cinnabar deposits of Steamboat Springs and 



' In my opinion miicli caution is necessary in using inferences from net structure. The system of 

 fissures so well known to litliologists as forming in olivine .loes not appear to be characteristic of that 

 mineral only, but of most substances which possess no distinct cleav.age. In the rocUs in which par- 

 tially decomposed olivine is found, it is often the only substance without a pronounced cleavage, and 

 under these circumstances such structure may of course be appealed to with eonfideuce; but, when 

 material is examined which has undergone at least two successive processes of radical alteration, it does 

 not seem to me any longer safe to judge from this structure alone. Indeed, I have met with many very 

 perfect examples of net stnicture in which it is certain that substances exhibiting it are not derived 

 immediately or remotely from olivine. 

 MON XIII 26 



