REPORT OF THE CHIEF ASTRONOMER 231 



SESSIONAL PAPER No. 25a 



Quartz 460 



Sodaorthoclase 29-1 



Biotite . e 22-0 



Oligoclase ." 1*5 



Magnetite - 5 



Apatite *5 



Calcite •* 



100-0 



The high proportion of quartz, the very low percentages of the alkalies, 

 yet lower than in Phase 1, and the low percentage of alumina indicate that 

 we have here again, as in Phase 1, a quite abnormal kind of granite. 



In the Norm classification this rock belongs to the sodipotassic subrang of 

 the domalkalic rang of the order, hispanare, in the dosalane class, with the 

 following norm: — 



Quartz 42-30 



Orthoclase 17-24 



Albite 16-24 



Anorthite 7-78 



Corundum 1-30 



Hypersthene •• 9-45 



Ilmenite 1*36 



Magnetite 1-16 



Apatite *31 



Calcite 1-40 



H 2 .. , 1-17 



99-71 



Neither rang nor subrang has yet received a distinct name in the system. 



Phase 3, collected at the point 50 feet from the upper sill-contact, is 

 unusually quartzose. It has nearly the same qualitative composition as Phase 

 2 but the structure is more like that of Phase 1, being essentially that of a 

 rather coarse-grained micropegmatite. The optical method gave the following 

 weight percentages for the different constituents : — 



. Quartz 57-1 



Sodiferous orthoclase 24-9 



Biotite 8-9 



Muscovite 3-2 



Calcite 2-5 



Magnetite 1-9 



Oligoclase 1-5 



100-0 



It is clear that there is notable variation in the composition of the biotite- 

 granite zone as represented in Phase3 1, 2, and 3. The apparently regular 

 increase in acidity in the zone from above downwards is fortuitous. The zone 

 is in reality irregularly streaked in many such phases, carrying variable pro- 

 portions of the mineral and oxide constituents. Whatever the cause, the 



