lHarvie] palaeozoic BRECCIA OF THE VICINITY OF MONTREAL 265 



amounts of chlorite, secondary quartz and epidote. The dyke rock, a 

 typical monchiquite, is dark coloured, having a fine-grained paste with 

 phenocrysts of biotite, augite and olivine, and containing in lesser amount 

 the same variety of fragments as the breccia. The augite occurs in well- 

 formed phenocrysts up to half an inch across. The colour, — pale green to 

 pinkish, and the high dispersion of the bisectrices, are characteristic of a 

 highly titaniferous variety. The olivine shows good crystal forms, but is 

 partly decomposed to hematite and carbonates. Biotite is quite abundant 

 in tlakes up to half an inch in size in the hand specimens, but very little 

 was seen in the thin sections. The groundmass consists of a mat of inter- 

 laced needles of augite. These are so closely arranged that there are no 

 email spaces left for the base; the latter only occurs in segregations or 

 patches. The base is a low refracting, glassy looking material, very 

 slightly anisotropic, — either glass or analcite, but more probably the 

 latter. A little acicular apatite is present. Octahedra of iron ore, pro- 

 bably magnetite, are very plentiful. A large grain of ilmenite was ob- 

 served in. the hand specimen, but it is considered to be a fragment as 

 none was found in the slides. 



Westmount Mountain. 



A breccia is found on the northeast end of Westmount mountain oc- 

 curring both in relatively large masses or plugs and also as the filling of 

 dykes. At Little's quarry an opening has been made giving a section fifty- 

 five feet high on the face, exposing several large masses of the breccia, a 

 breccia dyke, and also showing the relations of several dykes of other 

 material. At the Westmount quarry, to the northeast over the end of 

 the mountain from this last, the excavation has been largely in the 

 breccia showing it to have a depth of at least seventy-five feet. Between 

 these two quarries there are several other outcrops of breccia. The plan 

 on page — shows the relative positions of the various patches of breccia 

 and also a few of the more important dykes. 



Little's quarry furnishes the bulk of the information as to the origin 

 and relations of this group of occurrences. The most important features 

 are those shown by a large breccia dyke (slide î^o. 7), about four feet 

 wide and standing nearly vertical, which cuts the rear wall obliquely. 

 This dyke is an extreme phase of the breccia in which the paste or matrix 

 predominates, inclusions being rather infrequent. In its extension to the 

 north, it is connected with the patch of breccia occurring in that corner 

 of the quarry; whilst in the opposite direction it is probably connected 

 with the breccia showing in the west wall. The rear wall displays a 

 splendid section of the dyke and also of an offshoot from it which has 

 eroded or stoped out and filled a large cavity in the limestone. (See 



