THE PERSISTENCE OF WOLFRAM IN DEPTH. L >17 



out a vein from its outcrop, or following it in shallow drives under- 

 ground, can only continue doing so in the decomposed rock zone. 

 It is self-evident to anyone acquainted with Tavoy that it is impos- 

 sible to work a vein in hard undecomposed granite by the tribute 

 system alone as it exists there, and once the easily won ore is 

 removed, exploitation ceases and the vein is said to have " petered 

 out," or become too low grade to pay. The latter statement is of 

 course quite correct under prevailing conditions. 



After all, the existence or non-existence of wolfram at depth 

 is a matter which can only be settled by the experiment of driving 

 into the veins and examining them. We are not aware of any 

 reasons which would lead us to advise that such an experiment 

 is not worth carrying out. The theoretical arguments are rather 

 in its favour. There is a mine in Burma, which reproduces the 

 Tavoy granite conditions almost exactly, and it has been found 

 profitable there to mine wolfram and cassiterite at depths some 

 hundreds of feet below anything yet attempted in Tavoy. This 

 also should give encouragement. In OUT opinion tin; question of 

 the permanence of wolfram is of minor importance to that of 

 devising means of exploiting narrow veins in hard granite with the 

 labour supply available, and to extract it by a more modern method 

 than the knapping hammer and cradle. 



The world-wide association of wolfram with granite rocks is 

 remarkable. These rocks usually, if not always, contain free silica 

 and are of the lighter coloured varieties. The ores of tungsten 

 and tin also appear to be connected only with the upper and outer 

 parts of the intrusions, for, as we have pointed out earlier, it is 

 possible, when a considerable thickness of the granite has been 

 removed, for the veins to disappear altogether. What the inner 

 limit of vein extension, expressed in terms of feet, may be, we have 

 no means of ascertaining at present, though the problem is not 

 an insoluble one. In this connection, it is of ' interest to know to 

 what depths profitable deposits of wolfram have been worked in 

 other countries, with the reservation of course, that it by no means 

 follows that all Tavoy deposits will maintain similar values to 

 equal depths. When all has been said each case must be judged 

 on its own merits. 



At East Pool in Cornwall wolfram was most plentiful in the 

 Great Lode from the 140 to the 196 fathom level, that is from 840 

 to 1,176 feet and it has been worked to the 300 fathom level or 



