MetamorpJdc and Plutonic Rocks at Oineo. 1 1 3 



as is usual in 8ucli cases, this is associated with an exclusion of 

 iron, which has been deposited as magnetite adjoining them 

 and also in neighbouring fissures. Muscovite is in rather 

 more amount than the other mica in lath-shaped flakes. In 

 this mass are some minute crystalline grains, which ai-e 

 colourless, have a wrinkled surface, strong marginal total 

 reflection and polarize with red and green tints of the first 

 order of colours. I found one such crystal which had a 

 prismatic form, and which obscured parallel to the sides. 

 These data seem to indicate zircon. 



(6.) The schists here are a little more altered, and have 

 micaceous nodules. They are vertical on a strike of N. 80° W. 



(c.) Kather coarse schists having a gneissose appearance. 

 The strike is probably N. 60° W., the beds being vertical. 

 In a microscopical examination, I found this rock to be 

 composed of much quartz in grains, alkali mica in 

 aggregates of small flakes, together with a little brown 

 magnesia mica. 



A dyke crosses the beds at this place. The ground mass 

 of the rock was probably felspathic, but it is now greatly 



altered into a pale green-coloured fibrous chlorite, In this 



ground mass are a few much altered felspars, in which no 

 stria tions are distinguishable in more than traces. There 

 are also chlorite pseudomorphs after some mineral, possibty 

 augite. This dyke may be a porphyrite, but it is so much 

 altered that a satisfactory diagnosis is not to be arrived at. 



(d.) At this place the schists are in a still more altered 

 condition than those seen last on the line of section. They 

 have an appearance resembling that of a fine-grained gneiss, 

 and they strike N. 45° W. A sample of one of these schists, 

 when examined as a thin slice under the microscope, I found 

 to be composed of quartz and mica in about equal amounts, 

 but in places the former predominates slightly, while in 

 other places the contrary is the case. The quartz is in 

 angular grains of the character usual to some metamorphic 

 schists. It has very few fluid cavities, but it includes 

 numerous minute oval or rounded microliths of a brown 

 colour, which appear to be mica. The mica in this rock is 

 of two kinds, first a colourless alkali mica either in 

 individual crystals or in masses of flakes or small scales, 

 which are then surrounded by brown magnesia mica. 



Throuo;hout the slice there are masses of ii'on ore, which 

 in some instances are clearly aggregates of imperfect crj^stals. 

 These masses also include flakes of muscovite. 



