UTILIZATION OF THE WHITE PHOSPHATE 39 



the original deposits, and those which remain are merely the rem- 

 nants which have accidentally escaped erosion. 



41. Utilization of the White Phosphate. From the foregoing 

 description of the several varieties of white phosphate it will be 

 readily understood that this rock is not available for shipment 

 without undergoing some process of concentration. That a high- 

 grade product can be obtained by the proper concentration is 

 shown from the numerous analyses of selected hand specimens, 

 which sometimes show as much as 80 per cent, of lime phosphate. 

 Evidently the method of treatment should differ with the different 

 varieties. The analyses already given show that the stony variety 

 contains less than 50 per cent, of lime phosphate, and in it the 

 phosphate is so intimately associated with the silica that no ready 

 means of separating the two elements suggest themselves. In case 

 of the other two varieties, however, the problem of concentration 

 is a much simpler one. In case of the breccia, the properties which 

 may be taken advantage of in separating the chert and the phos- 

 phate are, first, differences in specific gravity, and, second, differ- 

 ences in hardness. It has been suggested that the two constit- 

 uents of the rock may be cheaply separated by some form of jig- 

 ging apparatus. Determinations of their specific gravity, how- 

 ever, do not offer much encouragement for this view. The chert 

 is found to have a specific gravity varying from 2.61 to 2.69. 

 The matrix of lime phosphate with which it is associated has a 

 gravity of 2.83 to 3.07. This difference of 0.3 or 0.4 is probably 

 not sufficient for any simple and cheap device. The specific 

 gravity of the lamellar variety is somewhat higher than that of 

 the structureless breccia matrix. 



The difference in hardness between the chert and the matrix 

 suggests the possibility of making a high-grade concentrate, 

 though not of making a complete separation of the two constit- 

 uents of the rock. As already stated, when long exposed to the 

 atmosphere the matrix becomes considerably indurated, so that it 

 is separated from the chert with great difficulty. Below the sur- 

 face, however, it seems probable that the phosphate will generally 

 be found soft and granular, so that it can be easily pulverized 

 and separated from the chert. The chert, on the other hand, shows 



