STRUCTURES AND CHARACTERISTICS OF TUNGSTEN DEPOSITS. 239 



with tliem usually fix a minimum of 1*6 per cent., but in the 

 absence of large scale st oping results, it is impossible to say at present 

 by how much this figure is in some cases exceeded. 



A table is given below in which the approximate composition 

 of the concentrates from 50 mines, all of which 



The cassiterito content pro( j ucec l e i t l, er \ ()i)V more tons during the 

 of Tavoy concentrates. l ** 



year 1918, is given. These mines prod'acea 



nearly 96 per cent, of the district's total output in that year. Cal- 

 culations have been made taking into account the individual produc- 

 tion of each mine for the year 1918, and the final result is that the 

 concentrates show an average composition of 54*32 per cent. W0 3 . and 

 18-8 per cent. Sn 0. 2 . This result does not differ much from the 

 figures given by Mr. C. Sutton, President of the Tavoy Chamber 

 of Mines, who lias stated : — " From the outbreak of war to the end 

 of 1918 we have exported 13,000 tons of concentrates, which I esti- 

 mate will have carried about 55 per cent, \\'0 3 . and 15 per cent Sn. 1 

 These figures do not represent the true composition of the 

 exported material, as a certain amount of mixed ore is separated 

 before shipment. They must also be regarded as approximate for the 

 following reasons : — 



(1) Some small mine owners could not furnish assay data -anc 



in a few cases an arbitrary figure had to be taken, based 

 on our general knowledge and the composition of con- 

 centrates from adjoining mines. 



(2) The ratio of the wolfram and tin content varies with 



the season, and the tin content is always higher in the 

 rains when water supplies enable ground-sluicing of 

 the detrital deposits to be carried on intensively, 

 In some cases it has been impossible to decide what 

 proportion of the total production is represented by 

 detrital won concentrates, compared with that won iron- 

 veins. 



The approximate percentage composition for 1918 must not be 

 taken as a basis for computing the average amount of tin ore in 

 any past or future year, for on various large mines its production 

 is controllable within certain limits, and naturally increases when 

 the world's market for the metal is good. 



1 Mining Journal March 16th, 1919, p. 155. 



