140 Mr. William Phillips on the Veins of Cornwall. 



Elvan. 



Elvan is one of the three grand dlsthictlons made In regard to 

 rocks by the Cornish miner. Whatever is not groiian (granite) or 

 kill as (schist), is of course with him elvan. So that, in fact, it is 

 extremely difficult to say what it is or even what it is not, with the 

 exception of granite and schist. The substance to which it is 

 most commonly applied occurs frequently in Cornwall, not as 

 forming tracts of country, but interposed between the schist, in 

 what is termed by the miner a channel. I know of no instance 

 of its thus occurring in granite. The situation of these channels is 

 not horizontal : they generally dip at various angles with the horizon, 

 and in various directions. The colour of elvan is bluish-grey, or 

 yellowish. It does not always disturb the contents of the metal- 

 liferous vein, which generally continues through it, though the load 

 is mostly narrower than when in the schist ; but it sometimes has 

 the effect of dividing it into small branches. By the accompany- 

 ing section^ of Pleasure, Fancy, and^ North Herland veins, PI. 8. 

 fig. 10. it will be seen that a large channel of elvan took a course 

 opposed, though not opposite, to that of the metalliferous vein, 

 and that two other channels took similar directions by the section 

 of the Manor Old Vein, fig. 11. The examination of some speci- 

 mens induced me to consider the elvan of these mines to consist 

 of crystals of quartz and felspar imbedded in compact felspar ; in 

 one specimen, the latter was intermixed with compact quartz. 



