86 



BUREAU OF AMERICAN ETHNOLOGY 



[bull. 52 



12. 541 



63.63 



9.91 



11.87 



0.62 



76. 17 



22.40 



99.49 



Ratios 



^, Sal 76. 17 7 5 



^1^^^ TW = 22:40<T>3 " 



^ J Q 12. 54 3 1 



^^^^^ F = 63:63<5>7 ^ 



Na^O' + K^O' .078 5 3 



^^^g iM = :079<3>5 3 



c, , K2O' .019 3 1 



S"^™g N^'= 7059 <5>7 4 



I. Scoria, near San Bias. J. G. Fairchild, United States Geo- 

 logical Survey, analyst. 

 la. Molecular proportions of I. 



This analysis places the rock in the siibrang Tonalose of the new 

 quantitative classification, a division in which many andesites and 

 diorites occur. Characteristic for the rock is the high percentage of 

 ferric oxide and low amount of FeO. This finds expression in the 

 red color of the rock. Except for this unusually high FcaOg, the 

 analysis is that of a normal andesite. 



Recapitulation 



THE LOESS SPECIMENS 



PetrograpMc microscopic features. — Characteristic of all the speci- 

 mens of loess in this collection is the relatively large amount of dis- 

 tinctly igneous material present. Fragments of quartz, plagioclase, 

 pyroxene, magnetite, and acid volcanic glass predominate and are, as 



