382 DEPARTMENT OF THE INTERIOR - 



2 GEORGE V, A. 1912 



granite. The stock covers about 1.5 square miles; its eastern contact run3 

 close to the smelter buildings, and for the purpose of distinction, the body may 

 be called the Smelter stock. 



This granite is a light flesh-pink to pinkish-gray, fine-grained rock, generally 

 massive but sometimes showing a parallelism among the constituents. Quartz, 

 feldspar, lustrous black amphibole, and dark-green pyroxene are discernible 

 in the hand-specimen. Each' of the last two is quite subordinate both in size 

 'and number of individuals. Under the microscope the feldspar is seen to be 

 very largely orthoclase, with a very small, accessory amount of plagioclase 

 which is probably a highly acid oligoclase. Considerable titanite in euhedra 

 and anhedra, and a little magnetite are the other accessories. The amphibole 

 is a pleochroic green hornblende; the pyroxene is a strongly coloured, green 

 monoclinic augite, apparently related in its optical properties to segerite. Of 

 three microscopic preparations of the rock not one gave sections favourable 

 for discovering the absorption scheme or angle of extinction of either mineral. 

 Both the femic minerals, where not granulated by pressure, are . greatly 

 corroded by the magma and always occur in a more or less scrappy condition. 



The structure is the typical panidiomorphic-granular, but a secondary 

 gneissic structure due to crushing has often been superinduced. 



The schistos-ity never approaches the perfection of that in the neighbour- 

 ing Cascade granite and banding was never observed. This aplitic hornblende- 

 pyroxene granite is, in age, almost certainly pre-Miocene and is probably post- 

 Triassic, but the evidence for a close dating of the intrusion is lacking. 



The specific gravities of three fresh specimens vary from 2i 626 to 2-652, 

 averaging 2-645. 



Attwood Series. 



As already noted, this name is proposed for the assemblage of metamor- 

 phosed sedimentary rocks which together compose the oldest series exposed 

 within the ' Boundary Creek district ' proper, unless we except the Grand 

 Forks schists and the Cascade batholith. This new name is taken from that 

 of Attwood mountain which is situated within the five-mile belt and is largely 

 composed of the rocks in question. These have been described by Mr. Brock 

 as follows (Report for 1902, p. 96) :— 



' The limestones, argillites and quartzites, cut by serpentines, form a 

 series which closely resemble the Cache Creek series (Carboniferous) of 

 the Kamloops district. They occur in areas of greater or less extent in 

 almost all parts of the district. They are always more or less metamor- 

 phosed; the limestone is generally white and crystalline, although occasion- 

 ally a core of black or drab limestone is to be seen; the argillites are or 

 were somewhat carbonaceous but are frequently altered. A hornblende 

 or mica schist found in the Long Lake region seems to be an alteration 

 form. Frequently both the limestone and argillites are altered by silicifi- 

 cation which, when complete, produces a quartzite-like rock. In the argil- 



