W. G. Foye — Nephelite Syenites of Ontario. 427 



Socialite was not shown in the slide examined. 



The nephelite often surrounds the albite and has apparently 

 replaced that mineral. A border of albite sometimes inter- 

 venes between the nephelite and microperthite. 



The hornblende resembles hastingsite. 



The ealcite is primary and occurs as rounded grains in the 

 hornblende or between the hornblende and nephelite crystals. 



No analysis of this type is obtainable. 



PAET II. 

 Suggestion Concerning the Origin op Nephelite Syenites. 



Professor C. H. Smyth, Jr.,* has suggested that the nephelite 

 syenites are segregated from a primary magma by means of 

 pneumatolytic gases. The pneumato lytic origin of nephelite 

 and sodalite has been advocated by a number of writers. Mier- 

 ischf and Lacroix;}: found that these minerals were sublimation 

 products within the cavities of limestone bombs from Monte 

 Somma. Lacroix states : — " The veinlets of orthoclase, soda- 

 lite, etc., traversing a doleritic leucite-tephroite, recall in a 

 striking manner veinlets of nephelite aplite which traverse the 

 essexites and nephelite gabbros of Madagascar, Brazil, etc." 



Brogger,§ in his study of the nephelite pegmatites of Norway, 

 found that nephelite was frequently altered to sodalite and 

 infers that the latter mineral was the result of the action of 

 hot sodium chloride solutions. Lacroix |j intimates that chlorine 

 and fluorine were influential in the formation of sodalite in the 

 nephelite syenites of the Los Archipelago. F. W. Clarke^f 

 considered the sodalite of the nephelite syenite type, litchfield- 

 ite, to have been formed at the expense of nephelite. 



J. Lemberg** produced sodalite from nephelite powder by 

 allowing it to stand six months on a water bath at 100° C. in a 

 20 per cent solution of sodium chloride. 



The accompanying black and white sketch (tig. 6) shows the 

 vein-like aspect of the sodalite in a nephelite syenite from Ice 

 River, British Columbia. ft It would be difficult to disprove 

 the pneumatolytic origin of the mineral in this case. 



*C. H. Smyth, Jr., this Journal, (4), vol. xxxvi, pp. 33-46, 1913. 



t Bruno Mierisch, Tseherm. Mitt., vol. viii. p. 188, 1887-88. 



i A. Lacroix, Mus. d'Hist. Nat. (Paris), Nouv. Arch., (4), vol. ix, p. 101- 

 102, 1907. 



8W. C. Brogger, Zs. Kryst., vol. xvi, p. 167, 1890. 



I A. Lacroix, Mus. d'Hist. Nat., (5), vol. iii, p. 98. 



«f[F. W. Clarke, this Journal, (3), vol. xxxi, p. 268. 



**S. Lemberg, Zs. d. d. Geol. Gesel.. vol. xxxv, p. 582, 1883. 



ft This slab may be seen in the geological laboratory of Harvard Uni- 

 versity. 



