124 Bulletin of Laboratories of Denison University. [Vo). xir 



which the above two have been derived. Epidote is usually- 

 regarded as a dynamo-metamorphic mineral, while chlorite is 

 usually given as a product of weathering. The origin of chlorite, 

 however, is sometimes closely associated with dynamic 

 agencies. It is not possible, therefore, to separate the prod- 

 ucts of the processes which have produced the degree of alter- 

 ation manifested in the rocks of this area. Without stating 

 more detail, vastly the majority of change in the rocks of this 

 area is due to dynamic action. 



A suite of specimens representing the fresh and decayed 

 rock were collected at the Anaconda mine in Virginia, a short 

 distance north of Virgilina, for illustrating the chemical changes 

 incidental to weathering. Here the decayed product is several 

 feet deep, the brown color of the decayed rock passing grad- 

 ually into the moderately fresh and firm green rock underneath. 

 In columns VI and VII of the table of analyses are given 

 chemical analyses of the fresh rock and its corresponding de- 

 cayed product. The decayed rock was of a pronounced yellowish 

 brown color, readily crumbling under slight pressure of the hand. 

 It effervesced very feebly in dilute acid, indicating hardly more 

 than appreciable traces of carbonates. When further digested 

 for some time in very dilute warm HCl, the brown coloring 

 matter was removed and the residue consisted of the usual 

 green mineral products composing the fresh rock. The per- 

 centage of residue composed of the green colored minerals was 

 very large. 



As indicated in the analyses of the fresh and decayed rock 

 of the table, the change has been one of hydration — the assump- 

 tion of water, accompanied by the preoxidation of the iron and 

 the partial removal of the more soluble constituents, lime, mag- 

 nesia, and alkalies. 



Age Relations. 



Excepting the northernmost extension of the Jura-Trias to 

 the south and southeast in the vicinity of Oxford, Granville 

 county, North Carolina, no known elastics of definite age are 

 found close to the area. Dikes of Mesozoic diabase are re- 



