F. D. Adams — Nepheline Syenite in Ontario. 15 



Good specimens have been obtained from lot 29 of range xin 

 and elsewhere, but on lot 25 of range xiv of Dungannon it 

 was found quite abundantly in what appeared to be veins and 

 irregular shaped lumps. From some of these, masses of pure 

 sodalite 10 by 10 by 1 inches in size were obtained, while con- 

 siderably larger masses could probably be secured by blasting. 

 It is probable that no other locality hitherto discovered in 

 America affords such large masses of this mineral, with the 

 possible exception of the nepheline syenite of the Ice River 

 in British Columbia. The sodalite is bright bine in color and 

 is often associated with strings of iron ore and traversed by 

 little reticulating cracks filled with a reddish mineral which 

 presents every appearance of a secondary origin and which 

 Dr. Harrington finds to be orthoclase feldspar. It is believed 

 that the sodalite may occur in sufficiently large masses to 

 enable it to be profitably extracted and employed for orna- 

 mental purposes. 



Summary. — The following points in connection with; the 

 composition of this nepheline syenite from Dungannon seem 

 to be especially worthy of notice. Nepheline is always very 

 abundant and in many large exposures the rock is an almost 

 pure nepheline rock, consisting of nepheline with a little horn- 

 blende or mica. This variety of the rock is really an Ijolite* 

 rather than a nepheline syenite. IS o orthoclase has been dis- 

 covered in the rock, although twenty -five thin sections have 

 been studied and some of them etched and stained. The con- 

 stituents of two specimens were also separated out by means 

 of Thoulet's solution. Its place is taken by an acid plagio- 

 clase, which in those cases where it has been examined has 

 proved to be albite. 



If the distinctive character of the variety of nepheline 

 syenite named Litchfieldite by Bayley,f be the replacement of 

 the orthoclase by albite, this rock is a more typical Litchfieldite 

 than that from the original locality. The propriety of defin- 

 ing nepheline syenite as a rock composed essentially of nephe- 

 line and an alkali feldspar instead of one composed of nephe- 

 line and orthoclase is also rendered evident, as otherwise it 

 would be necessary to classify this rock as a theralite from 

 typical specimens of which it would differ greatly in composi- 

 tion. Like the Litchfield rock also this Dungannon rock con- 

 tains neither augite nor sphene, but unlike it often holds 

 scapolite and calcite. 



Some years ago Prof. A. P. Coleman when investigating the 

 petrographical character of the bowlders of the drift in the 



* W. Ramsay and H. Berghell, " Das Gestein vom Iiwaara in Finnland." G-eol. 

 Foren. i Stockholm Forh., 1891, 304. 



f W. S. Bay ley, " Eleolite-Syenite of Litchfield, Maine, etc. Bull, of the Geol. 

 Soc. of America, 1892, 231. 



