WARREN. 



ALKALI-GRANITES AND PORPHYRIES. 



261 



13. Granite Porphyry, Quarr}', from east side of Rattlesnake Hill, Blue 

 Hills Reservation. Anal.yst, C. H. Warren. 



10. Fine Granite, Ruggles Creek, Quincy. 



14. Paisanite, Mosques Canyon, Apache Mountains, Transpecos, Texas; 

 A. Usann. T. M. P. M., XV, p. 439, 1895. 



The 



norm is as 



folk 



Quartz 



Orthoclase 



Albite 



26.64 

 28.91 

 36.68 



14 = 12.1 >f; Class 1. 

 92.23 Salic Minerals. 



Q 



*= .40< I > 7; order 4, quarofelic. 



Acmite . 46 



Diopside 3 . 45 

 Hypersthene . 76 

 Magnetite 2 . 32 

 Ilmenite . 61 



K;0 4- Na;0 

 CaO 



,60 Femic Minerals 



¥j9 _ 7 ^ 5 V. 3 



Na,0 



> x; Rang 1, peralkalic. 



7 < I > 1; Subrang 3; 



sodipotassic. 

 Liparose. 



The rock would, therefore, be termed a sodic-hornblende, aegirite- 

 granophyro-liparose. The phase with a dense groundmass found at 

 or near the contacts would be a graniphyro-liparose. 



The mineral composition for the porph^Ty has been calculated 

 approximately as follows (calculated to 100%). 



Granite Porphyry 



Ratio: Feldspar to Quartz 

 Porphyry Fine-Granite 



2.35 ' 2.84 



Albite to Microcline 



1.20 1.25 



54.5 Albite 55.6 



45 . 5 INIicrocline 44 . 4 



100.0 



10.3 



100.0 100.0 Microperthite 100.0 



In chemical composition the rock resembles closely the fine-granite. 

 It appears to be less feldspathic and more quartzose and slightly 

 lower in dark silicates. The mineral composition of the two in these 

 particulars is shown above in parallel columns. The microperthite 

 is closely similar in the two. The soda-iron silicates are, in the case 

 of porphyry, aegirite with some aegirine-augite, cataphorite and rie- 

 beckite and a little aenigmatite, while in the fine-granite only riebeckite 

 is present. This illustrates well how slight chemical difference to- 

 gether with different conditions during consolidation (as evidenced 



