COST OF GROUND FELDSPAR. 



29 



that tlu> linished product shall not become coiUainiiiated from the 

 contact with iron or steel. The production and cost of feldspar, 

 mainly for the use of the potteries, during five consecutive years, is 

 shown in the following table: 



Tamll IV. — I'rofl lief ion niid riiliic ttf feldspar, IDOl-lHOo.i 



[Short tons.] 



" Mineral Resources of the T'nited States, T'. S. Oeol. Survey, 1005. 



For fertilizer purposes the fine grinding of feldspar could be done 

 in iron mills similar to those Avhich are used for grinding limestone 

 in the cement industry. The only important points to consider would 

 be the i^ercentage of total potash present and the fineness of grinding. 

 At the present time there are few data availal)le on the cost of grind- 

 ing feldspar to a 200-mesh powder, but with modern machinery there 

 is little doubt that it can be done much more economically than would 

 have been considered possible only a few years ago. Under the 

 stimulus of the cement industry a great development has been made in 

 recent years in the methods and art of fine grinding. The following 

 table is of interest, as it .shows at a glance what the pota.sh in ground 

 feldspar would cost if the percentage is compared with a cost of gi'ind- 

 ing varying from $1 to $10 per long ton. 



Table V. — Price per pound of potash unit in feldspar. 



Potash contained 

 in the feldspar. 



Cost of ground feldspar per ton (2,240 pounds). 



3 per cent 



4 per cent 



5 jjer cent 



6 per cent 



7 per cent 



8 per cent 



9 per cent 



10 per cent 



11 per cent 



12 per cent 



13 per cent 



14 per cent 



15 per cent 



81. 



80.015 

 .011 

 .009 

 .007 

 .006 

 .005 

 .005 

 .004 

 .004 

 .004 

 .003 

 .003 

 .003 



85. 



80. 074 

 .055 

 .044 

 .037 

 .032 

 .028 

 .024 

 .022 

 .020 

 .018 

 .017 

 .016 

 .015 



86. 



.053 

 .045 

 .038 

 . 032 

 .029 

 .027 

 .023 

 .022 

 .021 

 .019 

 .018 



87. 



. 089 80. 104 

 . 067 . 078 



.062 

 .0.52 

 .045 

 .039 

 .035 

 .031 

 .028 

 .026 

 .024 

 .022 

 .021 



80. 119 

 .089 

 .071 

 .059 

 .0.51 

 .045 

 .039 

 .035 

 .030 

 .029 

 .027 

 .026 

 .024 



89. 



0.134 

 .100 

 .080 

 .067 

 .0.57 

 .050 

 .044 

 .040 

 .034 

 .033 

 .031 

 .029 

 .027 



810. 



80. 149 

 .111 

 .090 

 .074 

 .063 

 .056 

 .049 

 .045 

 .040 

 .037 

 .034 

 .032 

 .030 



The i^rices are given in cents per pound, so that if, for instance, 

 rock carrying 8 per cent of potash could be delivered for $9 per ton, 

 the potash contained in it would be added to the land at a cost of 5 



104 



