Ch. IX.] ON MINERAL AND METALLIFEROUS VEINS. 163 



CHAPTER IX. 



ON THE MINERAL AND METALLIFEROUS VEINS IN PRIMARY 



ROCKS. 



Our knowledge of veins very imperfect and too hypothetical the definition 

 of veins not correct. The following details on this subject entirely drawn 

 from Cornwall. Description of veins as seen on the sea-shore, in quarries 

 and similar open situations. Of small concretionary veins, of larger 

 veins not confined to individual rock-concretions, but traversing one or 

 more layers or strata. These commonly called contemporaneous and true 

 veins but are identical, only differing in size. Large quartz veins inter- 

 secting both the granite and slate, at St. Michael's Mount, at Mousehole, 

 and at Cape Cornwall. The connection between metalliferous veins and 

 the containing rocks. Veins curved both in their course, and underlie, as 

 at Polgooth and Huel Jewel mines. Veins intersect each other both in 

 their length and depth, accompanied by apparent movements, as at Dolcoath, 

 Weeth, Ting Tang, Huel Friendship, South Huel Towan, and Huel Peever 

 mines. Interference of veins and el van-courses, as at Polgooth and Dolcoath 

 mines. Veins similarly affected without the intervention of veins of any 

 description, as at Balnoon and Ding Dong mines. 



BEFORE concluding this sketch of the primary rocks, it is 

 requisite, in order to complete their description, to make a 

 few observations on the mineral and metalliferous veins by 

 which these rocks are traversed. The details on this subject 

 will be almost entirely drawn from Cornwall, where the 

 phenomena of veins have been more extensively and more 

 minutely investigated than in any other country ; .and, in- 

 deed, as far as works on this subject in our language are 

 concerned, Cornwall has been the principal source of in- 

 formation. The metalliferous veins contained in the secondary 

 rocks are not unimportant, either in an economical or scientific 

 point of view ; but to enter on their examination, at present, 

 would be departing from the plan of this work, and would, if 

 they were fully treated of, require an entire volume. Besides, 

 it is desirable that the subject of veins should^be carefully 



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