270 F. D. Adams — New Nepheline Rock. 



question which would serve as a type for the order. It is the 

 purpose of the present paper to make good this undertaking by 

 describing the first Ontarare. 



The nepheline syenites of eastern Ontario, while always pre- 

 senting the same general character, are represented by many 

 varieties. The rock is usually coarse in texture, while in some 

 of its pegmatitic developments the most extraordinary size of 

 grain is attained. In one occurrence near the village of Good- 

 erham in the township of Glamorgan, consisting of nepheline, 

 albite, and an occasional individual of lepidomelane, the nephe- 

 line masses — for the most part single individuals — are often as 

 much as three feet in diameter ; while in several other occur- 

 rences nepheline syenite pegmatites of almost equal coarseness 

 of grain have been found. The rock, furthermore, differs from 

 that of most nepheline syenite occurrences, in that it commonly 

 presents a more or less distinct foliation or gneissic structure, 

 which foliation is not due to crushing in situ with the develop- 

 ment of cataclastic structure, but is produced by a parallel 

 arrangement of the constituent minerals, which arrangement 

 seems to be a primary one or is at least unaccompanied by pres- 

 sure phenomena. 



The nepheline syenites of the region, furthermore, show a 

 wide variation in mineralogical composition, several varieties 

 often occurring together in the same mass, forming rude bands 

 which coincide in direction with the foliation, thus serving to 

 accentuate this and render it more pronounced. 



The iron-magnesia constituent which is most commonly pres- 

 ent is hornblende, represented by alkali-rich varieties, of which 

 hastingsite may be taken as a type.* Pyroxene, however, 

 replaces this in some cases and biotite in others. In some 

 places these minerals preponderate over the colorless constitu- 

 ents of the rock and in these varieties garnet locally occurs in 

 considerable amount. These dark bands, or schlieren, are, how- 

 ever, not very common and the prevailing facies of the rock is 

 one which is light in color owing to the abundance of feldspar 

 and nepheline. In certain occurrences other minerals which 

 usually play the part of accessory constituents — such as corun- 

 dum, sodalite, and cancrinite — attain more prominence, the first 

 mentioned mineral now being very extensively mined in an 

 occurrence of the syenite, near Combermere; while some of 

 the largest masses of sodalitef which have ever been found are 

 those which have been obtained from the nepheline syenite in 



* F. D. Adams and B. J. Harrington : On a New Alkali Hornblende and a 

 Titan if erous Andradite froni the Nepheline Syenite of Dungannon, Ontario, 

 this Journal, March, 1896. 



f B. J. Harrington : On Nepheline, Sodalite and Orthoclase from the Neph- 

 eline Syenites of Dungannon, Hastings Co., Ontario, this Journal, July, 1894. 



