320 C. H. GORDON 



alternating parallel lamella^ resembling eozoon and sometimes mis- 

 taken for it. 



The mica is usually confined to the portions showing a laminated 

 structure where it occurs in considerable amount along certain 

 planes. 



Titanite occurs in occasional grains, showing the usual chocolate 

 brown color and well-marked development of gliding planes parallel 

 to (221) characteristic of American sphenes.' 



The hornblende which is small in amount is compact and strongly 

 pleochroic. It is usually in close connection with the augite, and 

 the relations of the prismatic cleavages are sometimes such as to indi- 

 cate that the ortho- and clino.-pinacoids of the two minerals lie parallel. 



ORIGIN OF THE CANADIAN P\ROXENITES. 



Various opinions have been expressed as to the origin of the 

 Canadian pyroxenic rocks. Much has been written concerning the 

 origin of the apatite deposits which occur in them, but it is manifest 

 that any conclusion regarding these would be shaped, in part at least, 

 by the view held concerning the origin of the pyroxenites themselves. 

 The occurrence of the pyroxenites in bands alternating with the 

 quartzites and gneisses simulating bedding has led some writers to 

 regard them as of sedimentary origin. When first used by Dr. Hunt, 

 the term "pyroxenite" was applied both'to rocks which have been 

 recognized as intrusive, like those of Rougemont and Montarville, 

 and to the more or less massive beds or nests of pyroxene so often 

 intercalated in the so-called Archean limestones of New York and 

 Canada.^ 



Concerning the latter, Hunt states that they grade, on the one 

 hand, into granitoid orthoclase gneiss and, on the other, into hmestone, 

 and concludes that "these peculiar strata, which contain at the same 

 time the minerals of the associated gneiss and of the limestone, may 

 be looked upon as beds of passage between the two rocks. "^ They 

 were regarded by this author"* as having been deposited originally 



' G. H. Williams, American Journal of Science, Series III, Vol. XXIX, p. 486. 

 ^ G. H. Williams, American Geologist, Vol. VI (1890), p. 45. 

 3 T. J. Hunt, Geology of Canada, 1866, p. 185. 

 '' Chemical and Geological Essays, 189 1, p. 305. 



