278 QLTICKSILYER DEPOSITS OF THE TACIFIO SLOPE. 



open showed a rounded kernel of nnserpentinized rock within a shell two 

 inches or more in thickness composed of fibers of serpentine standing per- 

 pendicularly to the surfaces. These j)henomena seem to demonstrate that 

 the conversion of other rocks to serpentine has 

 been effected by the instrumentality of solutions 

 reacting on the material of the rocks. Tlie latter 

 are acid, and the solutions nuist have been mag- 

 nesian. Partially serpentinized shales also occur, 

 ^ „ „ ,• , ■ f but 1 have nowhere seen anV tendency to the 



Fin. 9. Serpenlinp formiiis fi i>m - i> i ^ v^ 



sandstone and composed of fibers f ^j.j.,^.^t|o,^ of Ij^lls iu tllis rOCk. Tllis faCt iudicateS 

 normal to the attacked surfaces. »<-'i"iiitiv. v^ 



that a portion of the constituents of the shale 

 resisted serpentinization so that replacement of the rock as a whole could 

 not take place, and only impregnation or the replacement of certain con- 

 stituents was possible. Not a trace of any olivinitic rock could be found 

 in Knoxville or its neighborhood, excepting the basalt, which is certainly 

 far more recent than the formation of serpentine and has suffered little 

 decomposition. 



Serpentine is attacked and removed by atmospheric agencies about as 

 rapidly as partially altered sandstones. "Where croppings of the latter are 

 serpentinized in part, sometimes the sandstone and sometimes the serpentine 

 may be seen standing in relief. On the whole, however, the serpentine 

 appears to offer least resistance to weathering. 



On the mip serpentinized and unserpentiuized metamorphic rocks are 

 laid dou-n in difierent colors. This division, however, must not be taken as 

 absolute. Traces of serpentine are to be found in the nnserpentinized area, 

 and there are many small masses of other metamorphic rocks in the area 

 colored as serpentinized. In the nature of the case an absolute division is 

 impossible, but the colors represent the limits within which serpentine is the 

 prevalent rock and serve to illustrate the approximate distribution of one 

 phase of metamorphism. 



Chromic iron is found in the serpentine here, as at many other places 

 in the Coast Ranges. At one locality, not far from tlie Royal claim, it forms 

 a series of nodules around which the serpentine has weathered away. The 



