31 6 BROWN & HERON: GEOLOGY AND ORE DEPOSITS OF TAVOY. 



minimum amount of fine-powdered mineral is produced. In the 

 bulk of Tavoy ores the wolfram and tin-stone are scattered in irre- 

 gular bunches throughout the vein matrix and these are often of 

 appreciable size. There are very few instances known in which 

 either of the minerals is evenly distributed through the quartz 

 in fine particles, and the few occurrences of fine acicular wolfram 

 ore are of no great economic importance. While a general scheme 

 cannot be laid down and final details settled without the results of 

 experience gained from experiment, we are definitely of the opinion 

 that concentration systems which make full use of hand picking, 

 coarse crushing, sizing and jigging, with the removal of wolfram 

 and cassiterite in every stage where they can be obtained as coarse 

 as possible, followed by full use of present practice as regards the 

 inevitable fine-ground minerals, are preferable to those methods 

 i ji which the unsorted ores are taken direct from the mine to stamps. 

 and reduced to powder before any attempt is made to separate their 

 valuable contents. 



Sufficient attention has not been paid on small mines to the 

 advantages of jigging after rough sizing. Up to the end of 1918 

 there was only one small hand jig in use on the field. We believe 

 that it would prove profitable to treat material that will pass a 

 I inch screen by this method and that with the water supply avail- 

 able on most mines of this kind, it would be possible to treat large 

 quantities of ore at a low cost. The method would also result in 

 greater savings than those obtained by crushing and panning. 



Sampling Surface Deposits. 



True placer deposits in the flat portions of the valleys are usually 

 sampled by boring, and as these operations present no greater difficul- 

 ties in Tavoy than are met with in similar deposits in other parts of 

 'he world, they need not be described here. 



Dee]) detrital formations at the foot of slopes generally contain 

 big boulders and beds of tenacious clay above the valuable pav 

 layers. On the hillsides the deposits are thin and, except in cases 

 where values continue down into decomposed granite, shallow pits 

 at regular intferrais <tre used for purposes of preliminary valuation. 

 On flatter ground the depth to be gone through may be anything from 

 10 to 50 feet, and, in extreme cases like Kanbauk, 80 or 100 feet 

 with a permanent water level about 30 or 40 feet down. 



