186 



University of California . 



(Vol. 3. 



I. Diorite, with some quartz. Pajaro. Reid analyst. 

 II. Diorite, finegrained. " " 



III. Diorite, Sehwarzenberg, Rosenbusch " Gesteinslehre." 



IV. Diorite, hornblende -rich. 



V. Augite diorite, Duluth, A. Streng and J. H. Kloos, "Crystalline 



Rocks of Minnesota," Neues Jahrbueh, 1877. 

 VI. Average of analyses of diorites, Pirsson, "Geol. of Little Belt 



Mts." U. S. G. S. 20th An. Report. 

 VII. Average of 14 analyses of diorites, Brogger, "Schrifter u.i Vid i. 

 Christ." 1895. 



VIII. Hornblende-gabbro, Duluth, A. Streng and J. H. Kloos, "Crys- 

 talline Rocks of Minnesota," Neues Jahrbueh, 1877. 

 IX. Hornblende-gabbro, Lindenfels, Odenwald, Rosenbusch, "Ges- 

 teinslehre." 



X. Gabbro -diorite. Maryland. G. H. Williams. 

 XI. Pegmatite. Pajaro. Reid anal. 

 XII. Aplite. 

 XIII. Rhyolite. 



Iii Table I, column I gives the analysis of the rock which 

 constitutes the main mass at Pajaro. It is lower in silica and 

 higher in iron than the average diorites. Column II gives the 

 analysis of the finer grained, more basic phase at Pajaro. It is 

 still lower in silica, and higher in iron, lime, and magnesia than 

 the typical diorites. The alkalies show but little change, too 

 small to be of importance. Columns XI, XII, and XIII give the 

 silica contents of the pegmatite, aplite, and rhyolite, respectively. 

 The great difference between the acidity of the dyke rocks and 

 their inclosing rocks is at once apparent. The other columns 

 give analyses of similar rocks taken for purposes of comparison 

 in the discussion of nomenclature. - 



The following Table II gives the calculated mineral composi- 

 tion of analyses 1 and 2 above. The feldspars are calculated as 

 AbiAiu. 



Table II. 





I 



II 



Hornblende 



55.59 



58.80 



Plagioelase 



39.96 



38.82 



Magnetite 



2.65 



2.40 



Apatite 



1.14 



.58 



Quartz 



66 



none 



Total 



100.00 



100.00 



