No. 4.] HARRINGTON — CANADIAN MINERALS, 253 



III. ON THE OCCURRENCE OF OLIVINE IN CANADA. 



The occurrence of olivine in the eruptive rocks of Rougement, 

 Montarville and Mount Royal, as well as in a doleritic dyke cut- 

 ting the Hudson River formation at St. Hyacinth, and in the 

 dolomitic cono'lomerate or breccia of St. Helen's Island, near 

 Montreal, was described by Dr. Hunt many years ago, and an 

 analysis of that from Montarville given. Recently it lias been 

 found in a number of other localities, and a few facts concerning 

 its occurrence at some of these are of sufficient interest to be 

 given here. 



Owing to the difficulty of navigating the Ottaw^a River below 

 the railway bridge at Ste. Anne's during the time of low water, 

 communication with a deeper channel than the one ordinarily 

 followed was deemed necessary, and was finally effected by cutting 

 across a ridoe of rock in the bed of the river. Coffer-dams were 

 built enclosing the required area, and when the water was pumped 

 out an excellent opportunity was afforded of seeing the bottom of 

 the river. The rocks exposed were sandstones and conglomerates 

 of the Potsdam formation, striking nearly east and west and 

 dipping to the south ^ijh°-4:^. Traversing these beds with a 

 course of N. 20*^ W., a vertical dyke about three feet thick was 

 found. It consisted of a rather fine grained uround mass holdins; 

 large plates of mica sometimes an inch or more across, irregular 

 masses and occasionally large crystals of black augite, and angular 

 masses of olivine occasionally more than an inch in diameter. 

 The last-named mineral gives the rock a very striking appearance, 

 as much of it is of a bright red colour. An analysis of this red 

 olivine o-ives the following results: — 



Silica 38-560 



Magnesia 44-369 



Ferric oxide 1-361 



Ferrous oxide 1 2-649 



Manganoiis oxide* 0-112 



Water (ign.) 2-914 



99-965 



It is, therefore, a variety with much less iron than that from 

 Montarville, which, according to Dr. Hunt's analysis, contains — 

 Silica 39-17, ferrous oxide 22.54, magnesia 39-68 = 99*39. 



When thin sections of the olivine from Ste. Anne's are exam- 

 ined with the microscope, the usual fissured or cracked appear- 



* With a little oxide of cobalt. 



