100 Notes on the Dressing of Tin Ore. 



" 4. It is necessary, in determining the degree of fineness to 

 which a mineral should be reduced, to consider the metal- 

 lurgical value of the ore contained in it, and set against this 

 value the loss which will probably be incurred, together 

 with the labour and expense attendant on the manipula- 

 tion. 



"" 5. The vein stuff should be reduced to such a degree of 

 fineness that the largest proportion of ' deads' (worthless 

 mineral) and clean ore should be obtained by the first 

 operation, thus saving labour and preventing the loss incident 

 to a finer subdivision of the ore and more extended treat- 

 •ment. 



" 6. The apparatus or plan of dressing may be considered 

 the most efficient which, with stuff of a given size, allows at 

 an equal cost the most perfect separation and of the proper 

 separation of stuff of nearly equal specific gravity. The 

 average percentage to which the clean ore is to be brought 

 and the highest percentage to be allowed in the waste being 

 determined, it is evident that the more perfect the degree of 

 separation the greater will be the amount of clean ore and 

 castaways (worthless mineral) obtained in each operation, 

 and the quantities of middles or stuff to be reworked will 

 be diminished. 



" 7. We may further consider a great improvement in 

 dressing operations, such apparatus or plan of working as 

 will allow, without a disproportionate increase in the cost, of 

 the equally perfect separation of fine and coarse stuff. This 

 will be of especial benefit in the case of finely disseminated 

 ore, which is necessarily obliged to be 'reduced to a great 

 degree of fineness.' Perhaps I should apologise for repeat- 

 ing the A B C of ore-dressing, but I fear that it has been 

 forgotten by many, and that until it has been relearnt many 

 good mines will continue to give poor returns." 



The treatment I propose for these hard ores, which con- 

 sist of very tough quartz, with more or less feldspar, mica, 

 tourmaline, and tin stone, is (1) Calcination, in heaps or 

 kilns ; (2) crushing in an ore or stone-breaker; (3) disin- 

 tegration ; ( 4) classification of disintegrated ore by a series 

 of sieves ; (5) concentration of the classified ore. 



I can, perhaps, best illustrate the success of this treat- 

 ment by giving the actual results obtained from a quantity 

 (about half a ton) of very hard ore from the Ben Lomond 

 district, Tasmania, kindly given for the trial by Mr. J. E. 

 Dobson, at my suggestion, and in the interest of Mr. C. W. 



