49 



ON THE ORIGIN AND DEVELOPMENT OF ORE DEPOSITS IN 



THE WEST OF ENGLAND. 



By J. H. COLLINS, P.G.S. 



Chap. III. — Eock Change as concerned in the Formation 

 OF Oke Deposits. 



Sec. 13, — On the localization of Mineral Substances in the 

 West of England Mining District* 



Group 3. Iron, Manganese, Nichel, Cohalt, Sfc. 



Iron in its various combinations is so abundant, not only in 

 tbe veins, but also in most of the rocks of the district, that it 

 might at first seem useless to consider its localization in connexion 

 with our present enquiry. Yet there are several prominent facts 

 which so markedly illustrate this localization as to claim our 

 attention. Everyone may see, for instance, that the kaolin 

 districts as a whole contain very little iron diffused through the 

 rock-masses ; in fact, china-clay and china-stone would be worth- 

 less if they contained any considerable proportions of this 

 element. Yet, some of the purest veins of red-hematite ever 

 found, occur in china-clay rock, as at the Euby Mine near St. 

 Austell, and near Hawkstor on Bodmin Moor. Moreover, there 

 are few masses of kaolinized granite known which are not some- 

 what closely associated with the highly ferruginous minerals, 

 schorl, and lepidomelane. 



The veins above referred to as existing in altered granitic 

 rocks are mostly cross-courses, running more or less in meridi- 

 onal directions. Many ferruginous cross-courses are also known 

 in killas districts, as for instance, those formerly worked at 

 Eestormel, Paw ton, and other places. There are, too, several 

 important east and west veins known which contain, at least in 

 their upper portions, large quantities of iron, the most notable 

 being the great Perran lode already referred to. In fact, the veins 

 of Cornwall could furnish considerable quantities of excellent 

 iron-ore were the price somewhat higher than it has been now 

 for some years past. Iron is, in fact, almost always abundant in 



* Continued from the Journal No. 39, p. 377. 



