CHAPTER IV. 



THE STRUCTURE OF RUBY HILL. 



Influence of granite on the Ruby Hill formations. The axis of fold of Ruby Hill, if 



such a confusedly uplifted mass can be said to have an axis of fold, has a 

 northwest direction from its point of junction with Mineral Hill, as the 

 northern end of Prospect Mountain is called. Mineral Hill is composed in 

 part of an outcrop of granite. The quartzite overlies the granite on its 

 northern side and bends around it to the east and west in the shape of a 

 horseshoe. The limestone touches the granite on the south and overlies the 

 quartzite, separating it on the surface on the east and west sides from the 

 granite. Although the granite does not seem to have broken through the 

 overlying formations, its presence may have had some influence ki deter- 

 mining the present position of the quartzite and limestone on this part of 

 the mountain, and from indications observed in the Richmond shaft (see 

 page 12), it is possible that it underlies the quartzite at no very great depth 

 in the Ruby Hill mines. Ruby Hill is separated from Mineral Hill by a 

 narrow divide and a deep l'avine which has been eroded in the quartzite. 

 This quartzite is found extending along the southwestern base of the former 

 hill and dips under it to the northeast; that is to say, it pitches northeast at 

 this point. On the east flank of Mineral Hill, on the other hand, the quartz- 

 ite dips to the east and on the western slope the quartzite also has a westerly 

 pitch. The limestone of Ruby Hill formed one and the same body with 

 that of Mineral Hill before erosion, and it is merely the continuation of the 

 long belt of limestone of which the greater part of Prospect Mountain is 

 composed. The bulk of Ruby Hill is made up of this rock, the shale only 

 making its appearance on the northeastern slope. 



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