QUARTZ-BEARING HYPERSTHENE-ANDESINE SYENITE 



219 



i 



MnO none 



BaO 



SrO 



100.59 



99.95 



II 



III 



IV 



0.05 





0.15 



none 





none 



0.04 







99.64 100.69 



I. Hypersthene granite, Saint Thomas Mount, Madras, India. 

 II. Hypersthene quartz diorite, Yercaud, Shevaroy Hills, Madras, India. 

 III. Norite, Saint Thomas Mount, Madras, India. 

 IV. Hornblende hypersthenite, Pammal Hill, Pallavaram, Madras, India. 



Norms corresponding to the Analyses of Rocks of the Charnockite Series on 



page 218 



(Calculated by Dr. H. S. Washington) 



I II III IV 



Q 41.22 20.95 



Or 24.46 6.67 5.00 0.56 



Ab . 24.10 31.44 26.20 4.19 



An 5.00 20.57 15.29 12.23 



Di '. 1.36 19.43 18.97 



Hy 3.34 13.74 20.27 42.35 



01 5.63 13.01 



Mt 1.62 3.25 3.71 4.41 



II 0.61 1.52 3.65 2.43 



Ap 0.34 0.67 



Classification 



Number. Symbol. Magmatic name. 



I I. 3'. '2. 3. tehamose 



II II. 4. 3. 4'. tonalose 



III III. 5. 3. 4'. camptonose 



IV IV. 1'. '2. 1. 2. hilose 



There appears to be remarkably close correspondence in mineral com- 

 position of the most abundant variety of charnockite of intermediate 

 composition and the Blue Bidge, Virginia, syenite. The principal min- 

 erals, andesine with orthoclase and hypersthene, and the nearly constant 

 presence of augite are identical in the two types. In the charnockite the 

 silica percentage is about 63.77, and in the Blue Bidge type an average 

 of five analyses (page 202) gives 63.89 per cent silica. Hornblende seems 

 to be more constantly present in the charnockite series, while both types 

 are alike in the irregular occurrence of biotite. 



Feldspar intergrowths are not so characteristic of the Blue Bidge type 

 as of the charnockite member, but are equally characteristic of the feldspar 

 members of the Nelson-Amherst counties, Virginia, comagmatic area, 



