GEOLOGY OF THE SAN JOSE DISTRICT 269 



CaO 11.85 10.78 



NajO 3.41 3.47 



K2O 2.35 1.42 



P2O5 trace 



Il20"o 06 .10 



HjO'S" 20 .55 



99.76 99.44 



9-30 



7.94 



3.01 



2.98 



1.27 



1.23 





.40 



.78 



.93 



100.30 



.17 01 





trace SO3 





.01 Li20 





100.28 



less for CI 



.04 



100.24 



I. Diorite, San Jose, Tamaulipas, Mexico. G. I. Finlay, anal. 



II. Diorite, diabasic facies, San Jose, Tamaulipas, Mexico. G. I. Finlay, 

 anal. 



III. Diorite, Rosetown, near Tompkin's Cove, N. Y. J, F. Kemp, Amer. 

 Jour. Sci., Oct., '95, 298. 



IV. Diorite, Electric Peak, Yellowstone Nat. Park. J. E. Whitfield, anal. 

 Monograph XXXII, Pai<; II, U. S. Geol. Surv., p. 116. 



The percentage compositions in standard minerals which give 

 the norm for I and II are as follows : 



I. II. 



Orthoclase 8.34 Orthoclase 13-34 



Albite 25.68 Albite 7.34 



Anorthite 31-97 Anorthite 28.36 



Nephelite 1.99 Nephelite 11.64 



Diopside 16.85 Diopside 24.40 



Olivine 3.36 Olivine 4.71 



Magnetite.. 3.25 Magnetite 9.28 



99.07 



Hematite 7.30 



98.74 

 HP .65 



99-39 



No. I is therefore salemose-limburgose, and No, II is sa- 

 lemose. 



B. PoRPHYRiTic Types 



As may be seen in the geologic map, Plate VIII, the town 

 of San Jose lies in the depression formed by the erosion of the 

 central portions of a laccolithic mass of andesite. The rock 

 is exposed continuously over twelve square miles of territory. 

 Throughout the laccolith it varies but little from the even- 



