246 BROWN & HERON. GEOLOGY AND ORE DEPOSITS OF TAVOY. 



very pessimistic on this subject. He divides the veins into three 

 groups as follows : — 



(1) those entirely in the metamorphic rocks, 



(2) those partly in these and partly in granite, 



(3) or those entirely in granite. 



Regarding the first group be writes, — " In no mine of this type 

 where ore-bearing veins are found over 500 feet up vertically above 

 the granite does the ore persist as far down as the contact." 1 



Our own knowledge of Tavoy mines leads us to conclude that 

 in no mine of this type have the veins as yet been followed down 

 to the granite contact by mining operations. This is certainly 

 not the case in the example quoted by Dr. Campbell. 



Hermyingyi is given as an example of the second group. Our 

 view is that sufficient development work lias not yet been conducted 

 at Hermyingyi to warrant a final conclusion that the average amount 

 of ore in respect of both number and width of veins diminishes in 

 depth, or that the average tenor of the vein stuff above the contact 

 is consideraby higher than it is below. 



With regard to the third case, veins which are entirely in granite 

 have naturally had their upper portions in the sedimentary rocks 

 removed by denudation, if they ever extended up into them. If 

 there are examples in the Talaingya valley which are worthless 

 in the metamorphic rocks and payable in the granite, this surely 

 is evidence of value increasing with depth. 



Dr. Campbell concludes. — " Persistence to a depth of 1,000 feet 

 has not yet been proved in any Tavoy vein and, while possible 

 in only a few cases, is improbable. In the great majority of the 

 veins already opened up values disappear at small depth. With 

 a few exceptions very little profit has been yielded by veins at a 

 depth of 200 feet. Unfortunately it must be admitted that not 

 only experience in the mines but deductions from the phenomena 

 of the occurrence of the ores compel us to regard the mineralized 

 zone in the Tavoy district as being of small vertical extent." 2 



It is something that Dr. Campbell admits the possibility of a 

 few veins in Tavoy persisting to 1,000 feet in depth. In the great 

 majority of veins opened up " values " may have disappeared at 

 small depth, but this is not the fault of the vein. Coolies gouging 



1 J. Morrow Campbell (10), p. 346. 



2 J. Morrow Campbell (10), p. 346. 



