348 E. H. Davison — Castle-an-Dinas Wolfrmn Mine. 



The hill rises 700 feet above sea-level, and forms a conspicuous 

 feature in the landscape ; it is surmounted by an ancient earthwork 

 which has given the hill its name. In 1915 the outcrop of a lode 

 was traced on the northern slope of the hill, and this has been 

 developed by mining operations and yields a remarkably clean 

 wolfram ore. 



Geological Structure of the District. 



In a paper read before the Eoyal Geological Society of Cornwall ^ 

 the writer described the general geology of the district, but since 

 then the development of the mine has been carried further and 

 fresh light has been thrown on the geological structure of Castle- 

 an-Dinas hill. 





INDEX 



MEADFOOT 

 SLATe. 



\y - 



GRANITE. 



\ 



Looe 



Sc4uE. A. 



J XDS 



Fig. 1. — Sketch-map of Castle-an-Dinas. 



The hill is mainly built of Meadfoot Slates, which strike 

 approximately east and west, and are folded on axes roughly 

 parallel to the strike. The hill lies within the metamorphic aureole 

 of the granite, and the slates have in addition been subjected to 

 intense pneumatolytic alteration, as a result of which the contact 

 minerals have been almost completely destroyed ; in one case, 

 however, the slates were seen to contain woUastonite. 



•" " The Geology of Castle-an-Dinas and Belowda Beacon " : Proc. E.G.S. 

 Corn., vol. xix. 



