138 



THE CKYSTALLINE ROCKS OF CECIL COUNTY 



It will be seen from the analysis which follows that in the fresh 

 rock there is not sufficient lime for the formation in such excess of 

 hornblende and epidote. 



CHEMICAL COMPOSITION. 





I. 



II. 



Si0 2 



...75.67 7 



3.69 



A1 2 3 



...12.28 12.89 



Fe 2 3 



... .85 l 



1.02 



FeO 



... 2.59 i 



3.58 



MgO 



... .37 



.50 



CaO 



... 2.65 



3.74 



Na 2 



... 3.63 



2.81 



K 2 



... .78 



1.48 



H 2 + 



... .29 



1.06 



H 2 - 



... .12 





Ti0 2 



. . . .29 





Zr0 2 



. . . none 





co 2 . . 



. . . trace 





P 2 5 



... .05 





so 3 







CI 



F 



S 



.11 2 



Cr 2 3 



NiO 







MnO 



... .18 





BaO 



... .07 





SrO 



. . . trace (?) 





Li 2 













Total. .. 



...99.93 9 



9.74 



RECALCULATION. 



Quartz 44.76 



Orthoclase 4.50 



Albite molecule ....30.57 

 Anorthite molecule. . 2.79 



Biotite 8.04 



Garnet 5.78 



Titanite 76 



Magnetite 1.21 



Apatite 12 



Misc 48 



Total 99 01 



Ab 12 Anj 



I. — Analysis of acid dike-rock. 



II. — Port Deposit granite-gneiss (quartz-monzonitesj. 



Analysis made by W. F. Hillebrand of the United States Geological Survey. 



1 The FeO figure includes the iron of pyrrhotite. Both this and the Fe 2 3 figure 

 are further in error by any reduction of the Fe 2 3 that may have resulted from the 

 action of H 2 S set free from the pyrrhotite. An exact determination of these errors 

 is impossible. 



2 Mainly as pyrrhotite. 



