ORIGIN AND DEVELOPMENT OF ORE-DEPOSITS. 289 



ground generally extends for a considerable width, shattering 

 and indeed obliterating the lodes to a great extent, although 

 now and then detached pieces, sometimes rich, are found in it 



in Herodsfoot it shortens (narrows) in depth, as 



in my experience I have found to be almost invariably the case 

 in the broken channels of ground of this kind.* The 

 " Caunting Slides " (N.E. and S.W.) of Penhalls probably 

 belong to this group. 



Class XIII. — Newer Cross-courses and Flucans. 



These usually contain more or less clay, especially where 

 they cut through a Killas country. Very often too, they contain 

 much crystallized quartz of the kind known as " cross-course " 

 spar, believed by the miners to be a sure indication of poverty as 

 regards ores of tin and copper at least. Not unfrequently there 

 is a good deal of brown hematite present, as in many of the so- 

 called " guides " of the St. Just district. 



The amount of faulting occasioned by these veins is 

 often very considerable. The "great cross-course" of the 

 Redruth district is an example. They appear to have been 

 formed after the deposition of the sulphuret ores had pretty 

 nearly come to an end in the respective districts. As examples 

 of veins belonging to this period (which however are probably 

 not of precisely the same age) the following may be given : — 

 proceeding from East to "West. 



1. — The flucan of slaty clay which crossing the lode 

 diagonally at Wheal Franco heaves it 16 to 20 fathoms to the 

 right. 



2. — The similar flucan at Wheal Robert, Sampford Spiney, 

 which heaves both cross-course and lode. 



3. — The great spar course at South Oaradon. Its contents 

 are chiefly quartz and earthy red iron ore. 



4. — The iron lodes at Restormel, near Lostwithiel, may be 

 provisionally placed in this group, although they are perhaps 

 much older. Here are two parallel lodes which have been 

 somewhat extensively worked upon at intervals over a range of 

 about two miles. The principal lode certainly can be traced 



* H. C. Salmon, Mining and Smelting Magazine, II, 213, 



