OF CENTRAL CANADA PART III. 171 



Garnet- Rock : Subordinate beds of this rock, composed essentially 

 of granular red garnets and crystalline quartz, occur among the 

 Laurentian strata of St. Jerome on the Ottawa, and Rawdon in 

 Montcalm county ; and also, according to Mr. Richardson, in asso- 

 ciation with micaceous schists at Baie St. Paul. Dr. Sterry Hunt 

 has likewise made known the occurrence of beds of more or less com- 

 pact and light-coloured garnet amongst the metamorphic series of the 

 Eastern Townships. See under " Garnet," Part II. 



Quartzite or Quartz-Rock : This rock consists normally of pure 

 crystalline quartz, either colourless, or of pale shades of red, yellow, 

 green, or smoky-brown. Coarse and more or less opaque varieties, 

 passing into quartzose sandstone and chert, exhibit various colours, 

 however ; and the rock is often green and greenish-grey from admix- 

 ture with chlorite. Some cherts are black from the presence of 

 anthracitic matter. Enormous beds of quartzite, frequently very 

 pure, occur in the Laurentian series of strata, as on the River Rouge 

 in the county of Argenteuil, and elsewhere; and these rocks are 

 still more characteristic of Huronian strata. Laurentian quartzose 

 conglomerates occur in the townships of Bastard and Rawdon ; and 

 a very remarkable conglomerate of the Huronian series, consisting 

 of pebbles of colourless quartz and red jasper in a colourless, green- 

 ish-white or pale-yellowish quartzose base, is met with in the Bruce 

 Mines district. These crystalline conglomerates show unmistakably 

 the metamorphic origin of the rock. Beds of chert and jaspery 

 quartz occur also in places on Lake Superior, and in the crystalline 

 region south of the St. Lawrence (see Part V). 



Siliceous Slate : This rock is probably an altered clay-slate. It 

 passes into impure quartz-rock or jasper; consists essentially of a 

 silicate of alumina; is hard or more or less slaty, and usually of a 

 greenish-grey colour, or dark green from intermixed chlorite, and 

 occasionally striped or zoned with lines of black, green, or red. Ex- 

 amples of siliceous slates are of common occurrence on the north shore 

 of Lake Huron, and amongst the Huronian strata of the Rive Dore* 

 and other localities on Lake Superior. In many places, these slates 

 hold rounded pebbles or masses of gneiss, syenite, &c., and thus form 

 " slate conglomerates." 



Augillite : This is one of the least altered rocks of the metamor- 

 phic series. It is simply a more or less indurated clay-slate, and 

 commonly presents a black or bluish-black or dark-grey colour, but 



