136 OBlGIN AND DEVELOPMENT OF ORE-DEPOSITS. 



a little more cassiterite it would have been reckoned as a part of 

 the lode. 



Balmynheer. This is another mine in Wendron where the 

 granite is impregnated with tin under but not over a "slide" 

 composed of clay, with a little quartz and mica, and about 6" 

 thick. " The tin-rock is a mixture of quartz, chlorite, gilbertite, 

 iron-pyrites, zinc-blende, tin ore, and a little wolfram." It is 

 from 20 to 30 feet thick, and has been worked to a depth of 30 

 fathoms from surface.'* (fig. 5, Plate in). 



South Wendron Mine adjoins the Lovell. The tin-ground here 

 (fig. 6, Plate in) is a very regular cylindroid of stanniferous rock 

 merging gradually on all sides into granite, with its axis dipping 

 at an angle of 49° from the horizon in a direction N. 25 W. 

 (true). The longer axis of the oval section of the pipe varies 

 from 20 to 60 feet, whilst the shorter is about 10 feet. The 

 mass consists of quartz, mica, gilbertite, a little iron pyrites, and 

 tin stone. The workings extend to a depth of 46 fathoms from 

 the surface, and consist of a shaft and a few 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 surround- 

 ing granite."! 



The deposits just referred to afford illustrations of a regular 

 series of impregnations and accompanying alterations of granite 

 rocks — commencing with a notable impregnation connected with 

 and starting from a master lode of considerable value (St. Ives 

 Consols), followed by examples related indeed to veins or joints 

 — at first stanniferous (East Wheal Lovell), then altogether 

 barren (Balmynheer), and finally reaching an example which 

 seems to be altogether unconnected with anything that can be 

 called a vein fissure. These modes of occurrence are illustrated 

 in plate in, figs. 2 to 6. 



In other districts these irregular tin deposits would be 

 spoken of as pockets, although they one and all lack one 

 character of a true pocket, since they do not appear to be 

 deposits in pre-existing cavities. 



*Ibid p. 648. 

 tibid p. 631. 



