3/02 



Notes on the Dressing of Tin Ore. 



portion of each of these classes, and obtained the free tin ore, 

 which he smelted, and has given me the following table of 

 results : — 



Mesh of Sieve 



Per cent. 



Per cent. 



Per cent. 



Per cent, of 



holding ore. 



of class. 



of tin in 



of tin on the 



return of tin 







each class. 



whole ore. 



in each class. 



T V inch 



... 135 .. 



. none, n 



early all quartz 



2" "O » 



... 30-0 .. 



. 3-81 



... 114 .., 



10-40 



Z }> 



... 14-0 . 



. 9-65 



... 1-35 ... 



12-30 



~o~0 » 



... 18-5 .. 



. 18-9 



... 352 ... 



32-05 



1 



Too » 



... 110 . 



. 23-62 



... 2-57 ... 



23'40 



Ore passing 



thro' 









Tiro inch 



... 130 .. 



. 18-9 



... 240 ... 



21-85 



1000 10-98 100-00 



These results show that in this operation we can at once 

 get rid of 13' 5 per cent, of worthless material, while we are 

 classifying the remainder into grades of equal-sized grains, 

 from which the clean tin ore may be separated with ease by 

 any of the washing processes. I should mention that the 

 average assay of this ore made by my assistant, Mr. Adams, 

 was 11 per cent, of tin, so that Mr. Morley's return of 10'98 

 per cent, of tin shows the separation to have been almost 

 perfect. 



This process is not suited to clayey ores, or ores associated 

 with hydrous minerals, such as brown iron ore, but with 

 quartzose or granitic ores I have no doubt that when com- 

 pared with the results of ijhe ordinary crushing and dressing- 

 plants it will be found to return much more and better dressed 

 ore for the smelter, a higher yield of metal, smaller require- 

 ments in space for machinery, less washing water, and lower 

 working cost. 



The ore classified by the sieves may be treated by dry 

 concentrators, a point of some moment in many districts 

 where water is scarce, or has to be brought long distances. 



