GEOLOGY OF THE SAN JOSE DISTRICT 



293 



Table II 





I. 



II. 



III. 



IV. 



V. 



VI. 



VII. ^ 



VIII. 



SiO^ 



.973 



.708 



1.038 



.762 



.800 



.808 



.880 



823 



AlA 



.198 



•173 



.182 



.181 



.206 



.186 



.203 



226 



Fefi, 



.011 



• 032 



.015 



.040 



.044 



.060 



.018 



017 



Fep 



•033 



.082 



.018 



.083 



.062 



.014 



.017 i 



027 



MgO 



.012 



.132 



.015 



.126 



.110 



.126 



.010 



on 



CaO 



.056 



.282 



.105 



.211 



.170 



• 193 



.oiS 



047 



Nap 



•113 



.069 



.080 



•055 



•053 



.056 



.160 



155 



K2O 



.057 



.032 



•037 



.024 



.021 



.015 



.052 



045 



Table III 



Na^O 

 K^O 



FeO 

 ^6303 

 NajO+KjO 



SiO, 



Nap 

 SiO, 



I. 



II. 



in. 



IV. 



V. 



VI. 



VII. 



1.98 



2.15 



2.16 



2.29 



2.52 



3-73 



• 307 



3.00 



2.56 



1.20 



2.07 



1.40 



•233 



1 

 .944 



.174 



.142 



.112 



.103 



.092 



.087 



.240 



.116 



.097 



.077 



.072 



.066 



.069 



.181 



VIII. 



3.44 



1.58 



• 243 



VII. CHEMICAL RELATIONS OF THE SAN JOSE 



ROCKS 



In Table I, page 292, are given the results of the eight anal- 

 yses which have been made of the San Jose rocks. The per- 

 centage composition by weight is indicated here for each oxide. 

 In Table II the molecular amounts of the oxides have been 

 obtained by dividing the percentage composition for each con- 

 stituent by the corresponding molecular weights. In Table III 

 the ratios for certain of the oxides when compared with other 

 constituents in terms of their molecular amounts in every case, 

 are stated. 



It will be noted, when the analyses which embrace nearly all 

 the rock-types of the district are examined, that the range in 

 silica between the most acid member, andesite, and the most 

 basic, camptonite, is not large. The nephelite syenite is more 

 acid than is usual with such rocks, and the tinguaites are more 

 basic. The type andesite is also poorer in silica than the aver- 

 age of many andesites. Alumina is high in every analysis. 



