150 Coleman — Nepheline and other Syenites in Ontario. 



grayer and not pleochroic. One or two large masses of 

 magnetite and serpentine probably represent olivines com- 

 pletely decomposed. 



2. The gray or purplisli gray variety, with relatively small 

 amounts of the dark ingredients, contains all the minerals 

 mentioned as belonging to JSTo. 1, with the exception of the 

 probable olivine; but the ferro-magnesian minerals are, of 

 course, less in amount, and occasionally a little brown biotite 

 occurs, in addition to the hornblende and augite. The red 

 color of spots in the rock is due to infiltration of iron oxide in 

 portions of nepheline completely changed to zeolites, and the 

 usual reddish or purplish tone of the rock is dne to the 

 general diffusion of the same oxide. As distinguished from 

 the previous variety this one is leucocratic. In some examples 

 tbe minerals have plate-like or long prismatic forms with a 

 suggestion of the trachytic structure. In one section the augite 

 is almost entirely replaced by hornblende, often dark brown in 

 the middle and green at the edge with very deep colors but 

 not strongly pleochroic, perhaps barkevitic in character. 



3. The porphyritic varieties of the nepheline syenite occur 

 partly a mile or two east of Port Coldwell and partly to the 

 south of the station near the harbor. Specimens from the 

 former locality are dark bluish gray, fine-grained, with por- 

 phyritic feldspar, nepheline (rarely) and hornblende crystals. 



One thin section from mile 819 shows very small crystals of 

 nepheline having the prism and basal planes, enclosed in ortho- 

 clase and possibly oligoclase, as well as in hornblende, the 

 latter mineral forming sieve-like structures, the holes being 

 filled with lighter minerals, a good example of poecilitic inter- 

 growths. The other minerals are augite, magnetite and apatite. 

 A second specimen shows less of the poecilitic intergrowths 

 but contains one or two long porphyritic prisms of nepheline. 



Porphyritic examples from south of the station have a 

 purplish gray ground in which bluish crystals of feldspar and 

 black crystals of biotite are embedded. The groundmass does 

 not differ much from the former rock, but the numerous 

 phenocrysts are orthoclase, oligoclose and brown biotite, having 

 strong dichroism. 



4. The fourth variety forms narrow pegmatitic veins in the 

 other varieties, and consists of the same minerals but of larger 

 dimensions, sometimes more than an inch in length, though 

 never rivaling the giant nepheline pegmatites of Eastern 

 Ontario, as described by Dr. Adams, with crystals more than 

 a foot long. The nepheline in the Port Coldwell specimens is 

 often changed to a turbid orange-red material, mentioned by 

 Sir William Logan as elaeolite,"^ the feldspars (orthoclase) are 



*deol. Can., 1863, p. 81. 



