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PETfiOGEAPHlC STUDY 



IB 



iron ore were widely disseminated through the glass. The refractive 

 index of the glass ranged from 1.52 to 1.545. 

 Chemical analysis. — 



5.43 



71.09 



16.23 



2.45 



1.61 



76.52 



20.29 



98.99 



Ratios 



rii Sal 76.52^5^7 tt 



^^"^^ Feln = 20T2-9>3<r --"" 



nA Q 5.43^1 . 



^'^'' F7Tm<7- ' 



Rang K^O-H-Na^Q-^^ 7 , 



^ CaO' .013 1 



c u K,0' .038 ^3^1 , 



Subrang ,^- = <->;; 4 



^ Na.O' .088 5 7 



I. Scoria, Miramar. J. G. Fairchild, United States Geological 



Survey, analyst. 

 la. Molecular proportions of I. 



Compared with the analysis of the tierra cocida, No. 263722, this 

 analysis presents several noticeable differences. The alumina is 

 lower, also the ferric oxide and the water, while the ferrous oxide 

 and alkalies are notably higher. Lime and magnesia are also slightly 

 higher. Considering this analysis as that of a fresh eruptive rock, 

 the calculation places the rock in the subrang Umptekose of Class II 

 of the quantitative classification. On comparing this analysis with 

 the others of this class listed in Washington's Chemical Analysis 

 of Igneous Rocks, the relatively low alumina and alkali content is 

 noticeable; also the relatively large amount of magnesia and of lime. 



