1892. J 



DAFERT AND DERBY — SEPARATION OF MINERALS. 



131 



Xenotime (sp. gr. 4.45 ±) 

 Titaniferous Iron, (sp. gr. 4.75 i:) 

 Monazite, (sp. gr. 5 ±) - 



Original 

 Sample. 



i8.5$g 



31-95 

 49.6 



Part I. 



26.5Ji 

 45 -o 

 28.5 



Part II. 



6.3^ 

 12. 1 

 81.6 



% To 

 Total in 



I. 



86. 55? 

 84.9 



34.7 



^ To 



Total in 



II. 



13.5^ 

 15. 1 

 65-3 



In another test on about three grammes of the same residue 

 screened between Nos. 4 and 5 bolting cloth (25 and 27 holes to a 

 centimeter) and withdrawn in three portions, light (I), medium (II) 

 and heavy (III), the result was as follows : 



Xenotime, 

 Titaniferous Iron, 

 Monazite, - 



j^ in I. ' ^ in II. 



7-5^ 



3-5 



4-1 



62.3^ 



59-5 

 15.0 



<in III. 



30.2% 



37-0 



80.9 



These results obtained at a si'ng/e operation with an improvised 

 experimental apparatus in which, from the lack of proper materials, 

 neither the regulating cock nor the spiral could be arranged to our 

 complete satisfaction, show very clearly the capabilities of the pro- 

 cess. It should be remarked that in the second table the showing is 

 not as good as it should be since part I contained a considerable 

 amount of lighter minerals (tourmaline, staurolite, limonite, musco- 

 vite and quartz) mingled with such fine fragments of monazite and 

 titaniferous iron, that no attempt at a complete separation by picking 

 out was made except for the xenotime. All the dark colored grains 

 in this portion were reckoned as iron and all the light colored ones, 

 not clearly xenotime, as monazite, so that the percentage of the 

 heavier minerals are altogether too high in the second column. Even 

 so, however, the percentages to the total of each mineral in this por- 

 tion are very satisfactory. The sand was a particularly difficult one 

 to deal with on account of the fragmentary condition of a part of 

 the monazite grains causing great variation in shape which impeded 

 the grading by size in the screens. 



It will be noticed that while the concentration of the monazite is 

 most satisfactory in the second operation, that of the lighter miner- 

 als is best in the first. This is due to differences (voluntary or other- 

 wise) in the manipulation of the draw-tube and shows the impossi- 

 bility of obtaining constant results owing to the personal equation of 



