170 



MINERALS AND GEOLOGY 



tains chlorite, with grains of magnetic iron ore and other minerals.. 

 The normal colour is dark green. Examples occur here and there in 

 connection with becte of crystalline limestone and iron ores of the- 

 Laurentian Formation, as at Calumet Falls on the Ottawa, and parts 

 of Madoc, Marmora, Tudor, and adjacent townships. In many cases 

 pyroxenite cannot be distinguished from hornblende rock ; and it 

 closely resembles also, in general character and composition, certain 

 eruptive masses and dykes belonging to the trappean series. Many 

 Laurentian pyroxenites, indeed, are probably of igneous origin. 



Amphibolite or Hornblende Rock : This metamorphic product is 

 sometimes described as diorite, but the latter term is properly 

 restricted to eruptive greenstones of similar composition. Horn- 

 blende Rock is composed normally of a mixture of hornblende and 

 soda-feldspar, but at times it consists of almost pure hornblende.. 

 Many varieties are also more or less calcareous, and in some, both 

 mica and quartz are occasionally present. These pass into syenitic 

 gneiss. The texture of the rock is compact, granular, fibrous or 

 slaty. The slaty varieties are commonly known as Hornblende 

 Schist, and the fibrous as Actynolite Rock or Schist. Examples 

 occur in some abundance among the Laurentian strata of Marmora,. 

 Madoc, Elzevir, Blythfield, and throughout the Laurentian country 

 generally, between the Ottawa and Lake Huron ; also at various, 

 places on Lake Superior, as at Point-aux-Mines, Goulais River, and 

 elsewhere ; but many of the hornblende rocks of these districts may 

 be really eruptive masses. Hornblendic rocks and slates form part 

 also of the crystalline deposits of Beauce and other districts of the 

 Eastern Townships. 



Wollastonite-Rock : The mineral Wollastonite (No. 64, Part II), 

 mixed with feldspar, pyroxene, quartz, calcite, and other minerals, 

 occasionally form beds in the Laurentian series, mostly in association 

 with crystalline limestone. Where the Wollastonite predominates, 

 the rock presents a granular-fibrous structure, and is white or pale- 

 greenish in colour. Examples occur in the counties of Argenteuil, 

 Terrebonne, Leeds, &c., but are comparatively unimportant. 



Epidote-Rock /This is also of subordinate occurrence. It consists 

 of a mixture of quartz and epidote, and presents both granular and 

 compact varieties, mostly of a pale-green colour. Examples have- 

 been recognized amongst the Shickshock Mountains of Gaspe ; and 

 others occur in Melbourne and other parts of the Eastern Townships. 



