1902] Barlow Nepheline Rocks of Ice River, B.C. 73 



amount of interstitial lighter coloured material (nepheline). It is 

 sprinkled all through with comparatively large and conspicuous 

 phenocrysts of honey-yellow sphene, 



II. A rock composed of hornblende, pyroxene and nepheline 

 with a very little felspar (anorthoclase or microperthite). This 

 last mineral, however, is in such small quantity that it must be 

 regarded as distinctly accessory (Ijolite, transition type). 



This rock is much lighter in colour and evidently less basic in 

 composition. It is irregularly mottled or spotted, owing to the 

 segregation of the coloured minerals leaving areas composed chiefly 

 of the lighter coloured nepheline. 



III. A rock composed essentially of hydronephelite (ranite) 

 biotite and iegirine. The hydronephelite is evidently secondary, 

 resulting from the alteration of nepheline originally present, so 

 that the rock may be considered as a biotite-aagerine-ijolite. It is 

 of a delicate pale red colour and might be readily mistaken at first 

 sight as an ordinary red syenite. 



IV. A rock made up of nepheline and felspar (chiefly micro- 

 perthite but also albite and a little oligoclase) in nearly equal pro- 

 portions with a smaller quantity of pyroxene, hornblende and 

 biotite and also abundant and comparatively large porphyrilic 

 sphenes (Nepheline Syenite). 



V. A rock composed mainly of felspar (chiefly microperthite 

 and albite) and sodalite with a little nepheline, biotite, augite and 

 aigirine (Sodalite Foyaite or Syenite). 



VI. A rock composed mainly of granular cancrinite and 

 segirine very much squeezed. The cancrinite is evidently second- 

 ary and derived from nepheline, which is also present. Sodalite 

 also occurs. (Canrcinite Syenite.) 



Besides these, which may be regarded as the integral 

 and important members of the parsnt plutonic, there are 

 dykes of Nepheline-Syenite-Pegmatite, and Tinguaite. These, 

 which are regarded as practically contemporaneous and differen- 

 tiates of the same magma, apparently cut the main mass in all 

 directions, filling up cracks formed during its cooling. The peg- 

 matite is composed chiefly of microperthite (made up often of three 

 felspars, orthoclase, microcline and albite) with varying amounts 



