236 BROWN & HERON : OEOLOG\ AND ORE DEPOSITS OF TAVOY 



small area does or does not contain veins until it lias been trenched 

 across the strike down to bed rock. On precipitous slopes such as 

 are associated with the transverse drainage in places where streams 

 breach the granite intrusions, wall-like outcrops of veins may be 

 seen, in situations too steep to permit soil accumulation or the growth 

 of trees, but even here they are hard to distinguish and very detailed 

 examination is required. The larger veins sometimes betray their 

 presence by dislocated blocks of quartz strewing a hill-side below 

 them, and these may be traced back to the general position of their 

 origin, but here again, the jungle growth renders an occurrence much 

 less helpful to the prospeetor than it would be in more open country, 

 for it cannot be detected from afar, and laborious search is neces- 

 sitated. In a general way the best way to prospect any given area 

 is to examine the stream beds first of all. The bare rock exposures 

 may reveal veins ; the presence of concentrates in the sands is an 

 indication that they may occur ; the existence of mineralised vein 

 quartz is a sure sign which by judicious exploration can be made to 

 lead back to the neighbourhood of the outcrop. The manner in 

 which even the connected upper portions of veins bend and accom- 

 modate themselves to the slopes of the hill-sides is unusual and 

 surprising, and, if not realised, is liable to lead to false deductions 

 causing unnecessary trouble and expense later. 



Exact data regarding the metallic contents of Tavoy veins are 



difficult to obtain. It is regrettable to have 

 Tenor or mineral con- , -, , . • , , , . , 



tent of Tavoy veins. *° record that on many mines worked by the 



tribute system, detailed figures of production 



are not kept. Even where they are, at best they can only furnish 



an inaccurate and underestimated result. Again, the irregular 



and erratic distribution of wolfram and cassiterito in pegmatites 



and veins of associated origin is another misleading factor, and 



valuations approaching the truth can in reality only be determined 



on such ore deposits from the milling results of large scale stoping 



tests. The following figures are given with these reservations. 



According to Mr. Maxwell-Lefroy : x — " A study of monthly out- 

 puts shows such contrasts as one mine working on lodes with 2*5 

 per cent, mineralization, i.e., of recovered wolframite, giving a 

 return of one ton of concentrate from 40 tons of quartz broken by 

 eight or fm men, and low-grade concerns with only 1 per cent. 



*E. Maxwell-Lefroy (20) pp. 12-13. 



