LACUNA CLAYS. 



By Alvin J. Cox. 



(From the La})Oratory of Inorganic and Physical Chemistry, Bureau 



of Science, Manila, P. I.) 



This investigation was undei-taken at the request of the Bureau of 

 Education to enable it to choose a clay for use in the pottery school, the 

 building for which is now being erected in Santa Cruz. None of the 

 clay deposits of Laguna Province have been thoroughly studied up to 

 the present time and, therefore, I will first discuss those so situated that 

 the stripping of the material would entail the least labor and the soil 

 overlying could easily be disposed of. Such clays would be economical 

 to use were they of high grade. 



A paper on the clays from the Island of Luzon has already been 

 published^ in which the uses and the chemical and physical behavior of 

 some of the Laguna clays and the influence of the fluxes were thoroughly 

 discussed. The data there given axe to a gTeat extent directly applicable 

 to the samples treated in this paper and the application is so simple that 

 the interested reader may make it for himself. The following statement 

 regarding kaolin may assist in the proper interpretation of the results 

 given below. 



The composition of pure kaolin (kaolinite) calculated from the 

 theoretical formula Al2O3.2SiO2.2H2O is — 



Per cent. 

 Silica (SiO.) 46.65 



Alumina (ALO,) 39.45 



Water (H,0) 13.90 



Total 100.00 



Examinations of kaolins from Harris Company, Webster, North Car- 

 olina,- and from Glen Allen, Missouri,^ are as follows : 



1 Cox, Alvin J., This Journal, Sec. 4., ( 1907 ), 2, 413. 

 = N. C. Geol. Sur. (1897), Bull. 13, .59 et seq. 

 »Mo. Geol. Sur. (1896), 11, 578 et seq. 



377 



