PRINCIPAL PHOSPHATE DEPOSITS. 



21 



limestone is known in the district as "calf's liver" {toie de veaii). 

 It is not workable in the natural state owing to its irregular com- 

 position, but over large stretches the gryphea lim.estone has been 

 altered and dissolved by the surface water which has left in situ, 

 as an insoluble residue, an argillo-ferruginous mud in which the 

 phosphate bed is represented by a layer of nodules cemented by 

 a gangue of a similar nature. In such conditions the phosphate 

 nodules may be exploited, for it is easy to separate them from the 

 substance with which they are mixed, by drying and sorting, followed 

 by washing. The thickness of the bed varies from 10 to 20 cm. 

 (4 to 8 inches), but this thickness sometimes reaches 30 and even 10 

 cm. (12 to 16 inches , whilst elsewhere the bed is lost completely and 

 ceases to be exploitable. The nodules are irregular in shape and 

 greyish- white or yellowish; they are soft, almost friable. Their 

 fracture shows grev spots with some blackish veins. Theii- size 

 varies from that of a hazel nut to that of the fist. They generally 

 have rounded edges, exhibiting a more or less angular shape. The 

 mass contains 20 to 25 per cent of nodules, and 75 to 80 per cent 

 of mud. The thickness of the mud or clinker which covers the 

 bed is verv variable, 4 to 3 metres (20 to 120 inches) at the most. 

 The Auxois nodules "contain 27 to 30 per cent of phosphoric acid, 

 equal .to 59 to 65 per cent of tribasic phosphate of lime. The 

 following are the results of three analyses by Delattre : — 

 TABLE IX.— ANALYSES OF AUXOIS PHOSPHATES. (DELATTEE.) 



Undetermined matter and loss 



Totals . . . . 



Equal to phosphate of lime . 

 Equal to carbonate of lime . 

 Equal to calcium tluoride 



Per cent 



•2-10 

 •2- 10 



27-00 



traces 



2-»i0 



l-7o 



85 -84 



traces 



2-40 



7 -So 



18-00 



IF. 

 Per cent 



1-60 

 2-50 



28-59 

 0-17 

 2-50 

 2-40 



B7-92 

 0-18 

 2-47 

 7-24 



14-40 



III. 



Per cent 



1-20 

 2-50 



■29-71 

 0-17 

 2-20 

 1-55 



38-08 



traces 



2-63 



7-45 



14-20 



99-20 

 0-75 



99-97 

 1-01 



^ 99-49 

 0-65 



98-47 

 1-53 



98-96 

 1-04 



98-84 

 1-16 



100-00 



59-07 



5-90 



3-59 



1 Totals to 99-69. 



