406 Eggleston — Eruptive Rocks at Cut ting sville, Vt. 



Minebal Deposits. 



On Copperas Hill (fig. 5) large bodies of pyrrhotite, 

 once mined as a source of copperas, have replaced lime- 

 stone cut by tinguaitic dikes which appear to have played 

 a determining part in the ore deposition. In this con- 

 nection, the presence of pyrrhotite, as an accessory min- 



Fig. 5. 



%*i 









.4 jjt'-i 



\0 ' J^^^^B 





■ 



■PJU&4TH1 



* d^*^*""*^ 









- [ 



. 







'£&* 



v* 





Ekj$^9 





Fig. 5. Copperas Hill, looking northeast, 

 pyrrhotite deposit at right center. 



Dumps from open cuts in 



eral in several of the rocks which have been described, is 

 worth noting. 



Molybdenite (M, fig. 1) occurs in syenite at its con- 

 tact with gneiss on the crest of Granite Hill, a quarter of 

 a mile north of the hornblende-syenite quarry. The 

 molybdenite scales are of medium size, often thickly 

 powdered, like the inclosing syenite, with yellow molyb- 

 dite. Apparently the deposit is too limited to warrant 

 development. 



GENERAL CONCLUSIONS 



Emplacement of Eruptives. — Cross-cutting relations 

 of the main eruptive body to the country rocks, the oval 

 surface plan, and high contact dips, indicate that the 



