MINING METHODS. 313 



Mill concoHUafet,:!! (58 per cent.of W0 3 ) 43-7 tons. 



(70 „ „ ) 25-35 tons. 

 Hand picked (71 per cent, of WO^) 8-02 tons. 

 Averago return of raino ore, 19 lbs.por ton. 

 Average assay of tailings, 7-1 lbs. per ton. (To per cent ore.) 



Up to 1917 the working of the mill was handicapped for want of 

 water during the dry seasons, and through fuel and power difficulties. 

 Mr. Griffiths has pointed out " that an improvement on these figures 

 is still possible and that a system of jigging followed by concentration 

 on tables will probably be adopted, by this means, it is hoped bhe 

 losses will be confined entirely to a much smaller percentage in the 

 shape of slime. The tailing has proved to contain only fine ore and 

 slime which could only be concentrated with difficulty and the quantity 

 of which could only be ascertained by the wet method. The losses 

 indicated comprised the W0 8 contained in tungsten ochre which 

 occurs in appreciable quantities in the decomposed portions of the 

 lodes, and which in any case could not be recovered in any concen- 

 trating plant. Taken altogether therefore the recovery cannot 

 be described as having been a failure." 1 



London and Burmese Wolfram Co:s Paungdaw Mill. — A small 

 sampling mill of three stamp batteries having 5 stamps each was 

 erected at this mine. The stamps are lifted by wooden axles and 

 cams, the shafts of which are rotated by a rope drive in two 

 sections, that is, each battery is actuated by a 31 foot Pelton wheel ; 

 the ratio of the drivers and driven being 1 to 5 twice over. 100 

 blows per minute have been obtained from this machine. It 

 was made on the mine of local timber, with the exception of 

 the stamp heads and the gudgeons of the cam shaft. The 

 wolfram is caught in long sluices and the tailings are subjected 

 to retreatment on perforated sluices which feed the fines on to 

 blankets. The blanket product is cleaned up in mechanically 

 operated bateas. The head of water which drives the whole installa- 

 tion is 135 feet. 



In the main mill, which is steam driven, the ore, delivered by an 

 aerial ropeway, is passed through a rock breaker of the Blake-Mareden 

 type to a storage bin. From the bin the ore passes to a revolving 

 trommel with 19 mm. holes. This is sprinkled with jets of water 

 from the outside. The oversize from No. 1 trommel drops into a 



l H. D. Gritliths(13)p. 214. 



