1 





2 





3 





63 



.70 



49, 



.20 



44, 



.10 



19 



.Y6 



35, 



.12 



40, 



.25 



13 



.61 





,12 



i 



.25 



2. 



26 





tr 





tr 





71 





tr 





tr 





tr 



14. 



,20 



15, 



,01 



CLAYS OF NEW YORK 499 



"With sucli treatment tlie ortLoclase yielded mxDre readily than 

 either albite or oligoclase. The foUo'wing analyses show the effect 

 of 96 hours' treatment of orthoclase with hydrofluoric acid at 

 60° F. 



Silica 



Alumina 



Potash 



Soda, ti 



Ferric oxid 



Water 



100.04 98.64 99.61 



From the analysis it will he seen that the composition of the outer 

 layer simply approximates that of kaolinite. 



1^0. 1 is the original feldspar. 



^0. 2 is inner layer of altered feldspar. 



'No. 3 is outer layer of altered feldspar. 



The artificial clay thus produced, when examined under the 

 microscope, resembled washed kaolin. It showed no hexagonal 

 scales, but contained a number of minute colorless cubes which are 

 supposed to be fluor spar. 



The theory advanced by Mr Collins was first suggested by Yon 

 Buch and Daubree, who believed that kaolinization is produced 

 by fluids containing fluosilicates or fluoborates acting from below, 

 generally, if not always, through fissures. (Annates des mines 

 20, 1841) 



Yon Buch early observed the constant occurrence of kaolin with 

 minerals containing fluorin, and suggested that the kaolin of Halle, 

 Germany, owed its origin to hydrofluoric acid. (Min. Tasch, 

 1824)^ 



Daubree considered that the kaolin near St Austell in Cornwall 

 must have had a similar origin. {Annates des mines 1841) 



1 The writer can state from personal examination that the Halle kaolins 

 were formed by ordinary weathering. 



