32 



THE ROYAL SOCIETY OF CANADA 



X X I Pegmoytlte, 



"Tl'i-rT^ H o r Tb h I e TtcLe rocK. 



Coarse granite . 



3 ri 



une 



r a, n It e 



section it is seen to consist of biotite, hornblende, feldspar and quartz 

 with accessory iron ore, apatite and zircon. The biotite occurs as 

 long shreds and irregular patches and forms about 5 per cent of the 

 rock. The hornblende which is pleochroic in shades of green occurs 

 in slightly smaller amounts. The feldspars consist of orthoclase, 

 microline and albite, the two former in about equal quantities, the 

 latter in smaller amounts. 



Intermingled with this fine-grained variety and apparently 

 cutting it is another phase with practically the saine composition and 

 microscopic character, but decidedly coarser grained. Its contacts 

 with the former type are quite sharp. 



Traversing both of these rocks is a dense, iine-grained black rock 

 whose relations are those of a dyke. It is 150 feet in length, 4 feet 

 in width, and everywhere presents sharp contacts against the red 

 granite phases and contains inclusions of them. A thin section of 

 the rock measured by the Rosiwal method shows it to consist of 35 

 per cent hornblende, 10 per cent biotite, 35 per cent feldspar and 20 

 per cent quartz. The feldspars are orthoclase and albite, the latter in 

 subordinate amounts. Accessory apatite, iron ore and zircon are 

 present. The rock accordingly differs from the granite chiefly in the 

 higher percentage of hornblende present. 



