ORIGIN AND DEVELOPMENT OF ORE-DEPOSITS. 113 



of England ; yet in a certain sense the belt of killas country near 

 the granite junctions may be regarded as analogous. 



Unstratified deposits will be considered in this chapter in a 

 slightly different order to that set down above, and, of course, 

 omitting those which are not clearly represented in our mining 

 region. Thus we have no really characteristic pipe-veins, 

 gash-veins, or contact deposits, although some of the ore-masses 

 present notable analogies to these. 



True segregated veins of metalliferous mineral are also 

 somewhat rare in the West of England, although there are 

 numerous examples of segregated non-metalliferous veins, of 

 hornblende, axinite, garnet, and especially of quartz. 



Well-marked pipe- veins — such as are common in the North 

 of England, are also unrepresented, though some of the pockets 

 and carbonas to be hereafter described present close analogies ; 

 typical gash-veins, such as those of the Mississipi valley, are 

 also rare,* but the tin-deposits at the Parka mines near St. Oolumb 

 are in many respects similar. 



Again, I do not know of any typical contact-deposits — 

 although it will be seen hereafter that many of the lodes are in 

 fact contact-deposits, lying between granite and killas or killas 

 and elvan for considerable distances, both in strike and underlie. 

 In a certain sense, too, the stoekworks at Oarclaze and Gariggan 

 may be looked upon as owing their mineralization to their 

 position of contact. 



Of stoekworks, impregnations, chambers or pockets, and 

 bedded veins or floors, the West of England presents excellent 

 and very instructive examples, and of rake-veins or lodes 

 proper, probably some of the best and most characteristic 

 examples to be found in the world. Examples of each of these 

 will be given in some detail in the following sections. 



Sec. 2.— Examples of Stratified Ore- Deposits. 



Mineral deposits formed in situ (c) and practically unaltered 

 since their first formation are, as already stated, not known in 

 the West of England — the stratified ore-beds which exist do in 

 fact invariably afford evidence of much re-arrangement, or local 



* Phillips' Ore-deposits, p. 93. 



