196 Canadian Record of Science. 



while the other again remained undissolved. We have here 

 probably an intergrowth parallel to the face of an octa- 

 hedron or rhombohedron. A similar intergrowth has been 

 described in the iron ore in the nephelinite of the Katzen- 

 buckel, except that here the titanic iron ore occurs in the 

 form of micaceous titanic iron ore, not as the coarse and 

 opaque variety found in the above mentioned rocks. 



It has been the invariable experience in Canada that the 

 large iron ore deposits in these anorthosite rocks contain so 

 much titanic acid that they cannot be profitably worked. 

 In order to determine whether the iron ore which is dis- 

 seminated in small grains throughout the whole rock was 

 also rich in this constituent, the iron ore of three hand- 

 specimens of the anorthosite from different parts of the 

 area was separated and tested for titanic acid. In every case 

 the mineral was but faintly magnetic and gave a strong 

 titanic acid reaction. 



Two specimens of iron ore from the pegmatite veins 

 wlich cut through the anorthosite and the gneiss at the 

 contact of the two formations, west of St. Faustin, and 

 therefore do not belong to the anorthosite, showed strong 

 magnetism and gave only a faint reaction for titanic acid. 

 The iron ore bed, a short distance west of St. Jerome, in the 

 orthoclase gneiss also consists of magnetite and contains no 

 titanic acid. We therefore find that these investigations 

 confirm the conclusion that the iron ore of the anorthosite 

 is very rich in titanic acid while the iron ore of the Lau- 

 rentian gneiss generally contains no notable quantity of 

 this substance. 



Pyrite. — A few small grains of pyrite often occur in the 

 thin sections of the anorthosite. They are generally found 

 associated with the iron ore. 



Apatite. — This mineral is seldom observed in the anor- 

 thosite. When it does occur it is in the form of more or 

 less rounded grains. It is more frequently found in the 

 varieties rich in iron ore in the Township of Wexford and 

 other localities, than in the normal anorthosite. 



Latterman in Rosenbusch, Physiographie der Massigen Gesteine, p- 786. 



