2i6 Bi(llcti)i of Laboratories of Dcnison University. [Voi. xii 



rounding clays is never entirely sharp, but a more or less grad- 

 ual transition from the clays to the pure ocher is usually shown. 

 The ocher-charged clays at the point of contact lessen consid- 

 siderably in the ocher-content a short distance away, and is en- 

 tirely absent from the clays at some distance from the point of 

 contact. As in the case of the ocher-bodies in the fresh rock, 

 the transition zone between the clay and the pure ocher is c|uite 

 variable, from a few inches or less to as many feet between the 

 extremes. 



The field conditions make it entirely plain that the position 

 of the ocher in the clays is in all respects similar to that in the 

 fresh rock. Evidence pointing to leaching or concentration of 

 these bodies upon weathering of the rock is lacking. Some- 

 what extensive mining on the properties of the Blue Ridge 

 Ocher Company, the Cherokee Ocher & Barytes Company, and 

 the American Ocher Company, affords the best opportunit}^ for 

 studying the mode of occurrence of the ocher in the residual 

 clays. 



Origin of tJic Ocher. 



The mode of occurrence of the ocher when viewed in its 

 relations to the character and structural conditions of the enclos- 

 ing rock forms the strongest possible argument for the theory 

 favoring its formation from solution. All evidence, both from 

 field- and laboratory-study goes to prove that the deposition of 

 the ocher has taken place, not by simple filling of cavities and 

 fissures in the rock, but by a molecular replacement of the orig- 

 inal rock. The principal evidence in proof of this is summed 

 up as follows : 



I. In nearl)^ every instance of exposure of the fresh rock 

 over the ocher-belt the rock is found to be extensively crushed 

 and shattered and cut in all directions with lines of fracture, 

 by compression. This mechanical action was more than prob- 

 ably accompanied by heat, and the zone of crushed rock af- 

 forded ready and natural passage-ways for underground circu- 

 lating waters, both of which were conducive or favorable to in- 

 creased chemical action. 



