CHEMICAL ANALYSES OE ROCKS. 



261 



Analyses of rooks from the Crandall volcano — Continued. 



Constituent. 



9 



10 



n 



12 



13 



14 



15 



16 



SiO ; 



57.26 



.76 



19.40 



2.49 

 3.29 



.16 

 2.57 

 5.68 

 4.21 

 2.95 



.51 



57.32 



.62 



17.29 



3.89 



3.03 



.06 



3.50 



5.81 



3.89 



3.04 



.50 



.10 



57.64 



.77 



18.43 



3.63 



2.84 



.10 



3.32 



5.49 



4.03 



3.33 



.34 



61.16 



.23 



16.17 



2.89 



2.18 



Trace. 



3.89 



4.26 



3.87 



3.20 



.13 



63.42 

 .35 



17.16 



3.09 



1.50 



.04 



1.64 



4.65 



4.51 



3.04 



.26 



.19 



63.97 



.48 



15. 78 



2.35 



1.87 



.05 

 2.84 

 3.71 

 4.36 

 4.01 



.40 

 Trace. 



64.40 



.40 



15.77 



2.47 



1.15 



.04 



2.12 



3.54 



4.10 



3.81 



.16 



.17 



71. 62 



.08 



14. 99 



1.27 



1.01 



.17 



.74 



1.33 



3.62 



4.81 



Trace. 



FeO 



MnO 



McrO 



CaO 



Na 





NiO 







Trace. 

 .51 







H,0 



Total 



.86 



.63 



2.09 



.44 



.58 



2. 24 



.41 



100. 14 



99.74 



100. 43 



100. 07 



100. 29 



100. 40 



100. 37 



100. 05 





9. Dioritic facies of gabbro; core, Hurricane Mesa, Crandall Basin (1436). 



10. Monzonite; east core, Hurricane Mesa, Crandall Basin (1442). 



11. Pyroxene-diorite-porphyry, approaching mouzonite-porphyry ; intrusive sheet, Hurricane Mesa, 



Crandall Basin (1372). 



12. Hornblende-mica-andesite-porphyry; dike, ridge south of Hurricane Mesa, Crandall Basin 



(1319). 



13. Quartz-diorite (tine grained) ; core, Hurricane Mesa, Crandall Basin (1414). 



14. Quartz-mica-diorite; core, Hurricane Mesa, Crandall Basin (1427). 



15. Quartz-mica-diorite-porphyry ; core, Hurricane Mesa, Crandall Basin (1423). 



16. Aplite; dike in core, Hurricane Mesa, Crandall Basin (1424). 



The chemical analyses show what is known of the composition of 

 the surface flows, dikes, and stock rocks of this district, exclusive of those 

 classed as absarokites, etc. Of these analyses, Nos. 1, 2, 3, 4, 5, 6, 7, 8, 

 9, 11, 12, and 16 were made by Mr. L. G. Eakins, and Nos. 10, 13, 14, 

 and 15 by the late Dr. W. H. Melville, in the chemical laboratory of the 

 United States Geological Survey. They are arranged according to the 

 increasing percentage of silica, which varies from 51.81 to 71.62. The 

 range of silica is greater than in the rocks of Electric Peak and Sepulchre 

 Mountain, most of the analyses showing less than 58 per cent silica. The 

 more siliceous rocks in both localities are similar. The variability of 

 the chemical composition of the rocks of this district has been discussed 

 in another place. 1 The analyses show that the basalts of the district vary 

 in composition within certain limits. 



'Iddings, J. P.,Tlie origin of igneous rocks: Bull. Philos. Soc. Washington, Vol. XII, 1892, p. 151. 



