SOUTH OF REDRUTH AND CAMBORNE, ETC. 



641 



the mine, the strike is about 22° N. of W., but to the W. the vein 

 turns round south and strikes W. 37° S., or even in some places for 

 a short distance S.W. ; it dips about 46° south, and is consequently- 

 very much natter than veins usually are in Cornwall, 70° being a 

 commonly accepted average dip. It has been wrought for a distance 

 of more than 300 fathoms along the strike and 160 fathoms in 

 depth. 



One peculiarity of the lode at Wheal Uny is that it lies at the very 

 junction of the granite and the killas ; and if looked at by itself it 

 might be considered an example of " contact deposit." However, 

 as the workings to the west show us a somewhat similar lode in clean 

 granite, it is evidently not necessarily connected with any pheno- 

 mena due to contact of dissimilar rocks. 



Fig. 1. — Section showing the Lode at Wheal Uny at th& ISO-fathoms 



Level. 



N S. 





A. " Leader." 

 E. Capel. 



B. Lode. 

 F. Killas. 



D. " Grreyback. 

 Gk Granite. 



The section (fig. 1) shows the appearance of the lode at the 130- 

 fathoms level. A is the so-called leader. In one part it is 18 inches 

 wide, consisting of a mass of fragments of more or less altered killas 

 (capel) with, some tin-oxide, and it soon dwindles downto a,merejlucan, 

 or vein of clay, with a little quartz, only 2 inches wide. The sides 

 (walls) are very smooth, presenting numerous slickensides ; in fact 

 this leader has all the appearance of being a mere crack, rilled in 

 the main mechanically by fragments of the sides reduced in places 

 to a clay by the attrition of the walls. 



B is the lode, a very fine-grained or compact bluish-grey schorl- 

 rock, with little spots or strings and veins of quartz, cassiterite, 

 chlorite, and iron-pyrites. 



D is a rock locally known as " greyback," or " black granite," but 

 not separated from B by any distinct line. It is a schorl-rock with 

 large grains of quartz in a compact black matrix. 



E is hard compact capel or schorl-rock. 



The killas, F, to the south, and the granite, G, to the north, are 



2u2 



