298 



REGINALD A. DALY 



averaging Ab 7 An 3 , as indicated by zero extinction on (oio). That 

 shell is surrounded by a still thinner, outermost shell, which gives 

 an extinction of about +5 on (010) and is either a more acid 

 oligoclase or else orthoclase. 



The ground-mass has a pilotaxitic to diabasic structure and 

 consists of plagioclase, augite, and magnetite, each in high pro- 

 portion. A few round granules of olivine may also be discerned. 

 The plagioclase is often zoned, with a somewhat larger relative 

 development of the acid shells. Again, the outermost shell may, in 

 many cases, be alkaline feldspar, but the very fine grain prevents its 

 actual demonstration. No sulphide mineral was visible in the rock. 



Mr. Steiger's analysis yielded the result shown in column 1 of 

 Table III. 



TABLE III 



Si0 2 . 

 Ti0 2 . 

 A1A 

 Fe 2 3 

 FeO . 

 MnO 

 MgO . 

 CaO . 

 Na 2 

 K 2 . 

 H 2 0- 

 H 2 0+ 



PA . 

 co 2 . 



BaO . 

 SrO.. 

 NiO . 



Cr 2 3 

 Zr0 2 . 

 S0 3 .. 



S. . . . 



Sp. gr. 



49.19 



.72 



100.59 



Calculated Norm of i 



Quartz 1 



Orthoclase n 



Albite 34 



Anorthite 20 



Diopside 6 



Hypersthene 6 



Ilmenite 5 



Magnetite 4 



Hematite 4 



Apatite 1 



Water, etc 1 



100. 27 



1 Andesitic basalt, lava flow at 11,000-foot contour of Mauna Kea. 

 id Molecular proportions in 1 . 



2 Average composition of norma! Hawaiian basalt. 



By the Norm classification the rock enters the dosodic subrang, 

 andose, in the alkalicalcic rang, andase, of the dosalane order, 

 germanare. 



