364 



QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 



material. Tt is accompanied by pyrite and quartz. Bitumen is also found, 

 especially in cavities in the opaline mass. 



The deposit of the Mt. Jackson seems to have been similar to that of 

 the Great Eastern, but of smaller extent. The explorations do not appear 

 to have been sufficient to decide whether there are or are not other similar 

 pipes of ove in this layer of rock. 



The following- cut (Fig. 17) represents a vertical cross-section of the 

 ledge upon which the ore pipe is projected : 



Fir.. 17. Vertical cro3a-section of the Great Eastern mine. Scale, 150 feet to 1 inch. 



Probable history. — Tlic dai'k, opaliuo Or chalcedonic "quicksilver rock" of 

 this locality seems to have resulted from a silicification of several rocks, 

 chiefly perhaps of serpentine. Both here and at the Great Western this 

 silicification seems to have preceded the deposition of ore, though somewhat 

 closely connected with it. The deposition of silica, in part amorphous, 

 probably succeeded a movement attended by the development of hot 

 springs. Renewed movements followed, dislocation taking place in the 

 opalized beds at the Great Eastern, close to those at the Great AVestern, 

 and these later movements were succeeded by the deposition of ore. This 

 interpretation of the structure is snp})orted by the existence of other ledges 

 of the opalized material in which no cinnabar seems to occur. 



