south: of eedettth and camboene, etc. 651 



honeycombed, and in the little cavities fine acicular crystals of 

 tourmaline may often be detected. The southern part of the pipe 

 is sometimes very granitic in appearance, and consists of pink 

 orthoclase crystals imbedded in a mass of quartz, chlorite, mica, 

 iron-pyrites, a little copper-pyrites, fluor, and tin-ore. I have 

 one specimen which is a true stanniferous granite ; for save a small 

 portion of iron-pyrites and tourmaline, it is made up entirely of tin- 

 stone, orthoclase, quartz, and mica. 



Eig. 10. — Plan of the Deposit at South-Wendron Mine. 





x * A V ^ 



■ v A V"' . *'* f '»''',*» *'" * 





jSwzZc aco 



"goEeet. 



G G. Granite. 0. Tin-bearing rock. 



The workings extend to a depth of 46 fathoms from the surface, 

 and consist merely of a shaft and a few very short levels or lateral 

 excavations. 



The characteristics of these three deposits may be summed up 

 in a very few words ; they are masses of stanniferous rock passing 

 gradually into the surrounding granite. The fact of this passage 

 and the presence of the pseudomorphs justify us in concluding that 

 the so-called lode at the Lovell mine was once granite ; and if this 

 is admitted, we can have no hesitation in affirming that the Bal- 

 mynheer and South-Wendron deposits were formed by the alteration 

 of the same rock. 



IY. Definition op the Teem Lode oe Mineeal Vein. 



The terms lode or mineral vein, commonly regarded as synony- 

 mous, are usually taken to mean the mineral contents of a fissure. 

 Thus Mr. Carne says *: — " By a true vein I understand the mineral 

 contents of a vertical or inclined fissure, nearly straight, and of indefi- 

 nite length and depth." In Prof, von Cotta's ' Erzlagerstattenlehre ' 

 (p. 102) we find the definition " Erzgange sind Spaltenausfiillungen 

 welche Erze enthalten ; " and similar explanations of the term mi- 

 neral vein are constantly met with. 



* Trans. Eoy. Geol. Soc. Cornwall, vol. ii. p. 51. 



