684 



CROSS, IDDINGS, P IRS SON, WASHINGTON 



pyroxene, for the reason already given. The resulting constitu- 

 ents reduced to molecular proportions may be distributed among 

 salic and femic minerals as shown in the accompanying Table X. 

 From these data we deduce the standard mineral composition 

 of the rock from near the Parrot vein as follows : 



table x. 



SiO g . . 

 A1 3 3 . 

 Fe 2 3 . 

 FeO... 

 MgO.. 

 CaO... 

 Na 2 . 

 K.O.. 

 H s O- 

 H 2 + 

 Ti0 2 .. 

 P 2 5 .. 

 MnO • . 

 BaO... 



CI 



F 



Alb. 



FORMULA. MOL. WT, 



Si0 2 49 X 60 



K„0~.Al„0,.6SiOo - - - 11 X 556 



NaoO.ALO3.6Sid., - - - 1 X 524 



CaO.ALO3.2SiO., - - . - - 6 X 278 



CaO.Si0 2 - - - - - 6 X 116; 



MgO.SiOo - - - - 4 X 100 



FeO.SiOo" 2X132. 



MgO.SiOo - - - - 47 X 100 1 



FeO.SiOo 17 X 132 ' 



FeO.Ke.O3 - - - - 5X232 



KeO.TiO, 6 X 152 



CaKo 2 X 94 



Diop. 



Hyp. 



64 



16 



47 



Minus 

 Qu'rtz 



- 49 



Percentages Determined from Rock. 



Readjustments. 



Standard Mineral Composition. 



Quartz. 22 



Orthoclase 17 



Plagioclase 42 



Biotite 9 



Hornblende 4 



Pyroxene 2 



Magnetite 



Pyrite 



—2-94 



-f 6.12 



Albite 24.71 -j- -5 2 



Anorthite 17.76. -{-1.67 



Diopside 1 .36 



Hypersthene. ... 6.94 



Fluorite .19 



Ilmenite .91 



+1.16 



Quartz 19.61 



Orthoclase 23.69 



Albite 25.23 



Anorthite 19-43 



Diopside 1 .36 



Hypersthene 6.94 



Fluorite 19 



Ilmenite 91 



Magnetite 1 .92 



Pyrite 07 



99-35 



