OF CENTRAL CANADA PART II. 105 



54. Hypersthene : Brown, brownish-biack, brownish-green ; with 

 pale-grey streak, and a more or less pearly-metallic lustre. Mostly 

 in laminar or foliated masses. H = 5.0 6.0 ; sp. gr. 3.3 3.42. 

 BB, gives a black magnetic bead. Essentially a silicate of magnesia 

 and iron oxide. A specimen from Chateau Richer yielded Dr. Sterry 

 Hunt : silica 51.35, alumina 3.70, protoxide of iron 20.56, lime 1.68, 

 magnesia 22.59, volatile matter 0.10. Occurs in association with 

 anorthosites or feldspar rocks, more especially in Chateau Richer 

 and St. Urbain, near Baie St. Paul, below Quebec. 



(4) GROUP OP CHRYSOLITIC SILICATES. 



[The minerals of this group are essentially silicates of magnesia, 

 the latter base being more or less replaced, however, by protoxide of 

 iron. Sp. gr. 3.1 3.5. Infusible. Gelatinizing in heated hy- 

 drochloric acid.] 



55. Chrysolite or Olivine : Yellow, green, brownish-green. 

 Rhombic in crystallization, but rarely occurring otherwise than in 

 small grains and granular masses imbedded mostly in eruptive rocks. 

 H = 6 7 ; sp.gr. 3.3 3.5. BB, loses its colour but remains 

 unfused, except in the case of certain highly ferruginous varieties not 

 yet found in Canada. The powder becomes decomposed, with 

 separation of gelatinous or flocculent silica, in both hydrochloric and 

 sulphuric acid. This species occurs in the trap mountains of Mont- 

 real, Rougemont, and Montarville, usually in the form of small green 

 and yellow grains, but occasionally in indistinct crystal-masses. An 

 analysis by Dr. Sterry Hunt yielded: silica 37.17, magnesia 39.68, 

 protoxide of iron 22.54. 



56. Chondrodite : Yellow, brownish-yellow. In small granular 

 masses, mostly imbedded in crystalline limestone. H = 6.0 6.5 ; 

 sp. gr. 3.1 3.25. BB, infusible. Gelatinizes in acids. Consists 

 essentially of silica, magnesia, and fluoride of magnesium ; or is an 

 oxygen compound with part of the oxygen replaced by fluorine. 

 The latter element appears to vary in amount from about 2^ to 

 nearly 10 per cent. Chondrodite occurs in many of our crystalline 

 Laurentian limestones, frequently accompanied by scales of graphite. 

 Newboro', in the township of North Crosby, in Leeds County ; 

 Grenville, in Argenteuil County ; and St. Jerdme, in Terrebonne 

 County, have yielded examples. 



