404 



cox. 



Variability. — These few tests show that physically the tuff occurring 

 throughout the Philippines is very variable. When no attention is paid 

 to its selection it may be good or extremely poor and this is why it has 

 fallen into disrepute. With the selection of a good quarry, this stone 

 should be valuable, especially because of its accessibility and the ease 

 with which it is worked. 



CHEMICAL EXAMIlvTATION". 



The chemical constitution of several samples of Philippine tuffs and 

 their close relationship to the igneous rocks is shown by the following 

 analyses : 



Table VII. — Analyses of Philippine tuffs and igneous rocks. 



[Figures give percentages.] 



Source. 



Silica (SiOo) 



Alumina (AI2O3) 



Ferric oxide (FenOa) 



Ferrous o.xide (FeO) 



Lime (CaO) 



Magnesia (MgO) 



Soda (Na«0) 



Potash (K.;0) 



Loss on ignitions 



Water (H;0) (below 



105-110°) 



Titanic o.\ide (TiOo) 



Manganese oxide (MnO)_ 



Total 



Tuff from- 



Man- 

 ila.« 



56.84 

 18.46' 

 0.75 

 2.51 

 4.78 

 1.59 

 4.12 

 2.72 

 6.95 



1.76 



(") 

 trace. 



100.48 



Guadalupe. 



56.65 



22.34' 



1.87 



4.74 

 2.36 

 2.38 

 2.84 

 4.86 



2.51 



100. 44 



59.27 

 17.06 

 2.16 

 2.61 

 3.37 

 1.52 

 2.49 

 3.63 

 6.42 



1.34 



0.88 



trace. 



100.70 



Majay- 

 jay. 



57.26 

 16.95 



7.55 



3.56 

 1.10 

 1.64 

 1.86 

 7.65 



1.43 

 0.91 

 0.23 



Igneous rock from — 



Malaqui, 

 Taal 

 Volca- 



Aroroy, 

 Masbate.' 



53.81 

 19.69 



8.16 



7.73 

 3.13 

 3.64 

 2.19 

 2.13 



0.24 



C) 



100. 72 



Canlaon Volcano. 



2.6 

 4.C 

 2.1 

 l.; 



0.1 



99.87 



North 



rim of 



new 



crater. 



53.69 

 18.00 



9.11 



8.64 

 4.59 

 3.07 

 1.63 

 1.08 



0.31 



100. 12 



South- 

 west 

 slope 

 of old 

 crater. 



55.97 

 20.35 



6.26 



7.92 

 3.40 

 3.52 

 2.48 

 0.38 



0.33 



C) 



100.61 



'^ Equal portions of the three samples given in Table I were mixed thoroughly, pulver- 

 ized, air-dried and analyzed. 

 •> Sample collected in 1906. 

 •= Sample collected in 1908. 



^ Average of two very closely agreeing independent samples, probably dolerite. 

 ^ Average of two very closely agreeing independent samples, probably andesite. 

 'Includes titanic oxide (TiOo). 

 s Mostly water (H.O) above 105-110°. 

 ^ Included in alumina. 



CEMENT. 



I first analyzed the Philippine tuff in the early part of 1907. Its 

 composition is nearly the same as many of the clays and shales used 

 for cement manufacture. Since then I have had hopes that it might 

 be used as a cement material and have expended considerable effort in 



