G. F. Harris — Journey through Russia. 



Ill 



Under the microscope this gneissose rock presents evidence of great 

 strain and mechanical movement. The quartz, the most abundant 

 mineral present, has been crushed to such an extent as to assume 

 a cataclastic structure, and nearly all the fragments shovs^ character- 

 istic mechanical deformation. In addition, the fragments have been 

 arranged in closely packed layers, and where the shearing proved 

 too great for them they have been broken through along these 

 layers ; in the undulating cracks thus formed mica occurs in some 

 abundance. It is this structure which renders the rock so distinctly 

 foliate. Felspars are not common in my hand-specimens, and those 

 present are also much broken up. In o.ne micro-slide, however, 

 I find a rather large fragment of a triclinic felspar, much altered 

 by crushing ; it is too far gone to enable it to be satisfactorily 

 determined, but presents the general features of microcline. This 

 comparatively large fragment forms the nucleus of a lenticular, 

 augen-like structure, bounded for the most part by mica, interrupted 

 here and there by minutely crushed quartz which invaded the 

 nuclear area. Many of the quartz fragments in the rock exhibit 

 secondary enlargement. 



This gneissose rock at Siuro occurs near the junction of mica- 

 schist with an immense «^ass^y of porphyritic granite. 



The next section we examined was in the railway cutting, a little 

 to the west of the station of Suoniemi, where the Pre-Bothnian 

 mica-schist is well exposed. This rock presented no points of 

 special interest. It is reddish-brown in colour, fine-grained, and 

 well foliated. In thin sections, under the microscope, it is found 

 to consist of deformed angular fragments of quartz interspersed 

 amongst orientated minute films of sericite. Large masses of 

 muscovite occur in blocks by the side of the railway, but I did 

 not see them in situ. 



Fig. 3. — Section in a "leptite" quarry, Mauri, Finland. 



A railway cutting near Kulovesi showed an indescribable mixture 

 of schist and small veins of granitic rock, on the top of which were 

 a few feet of glacial clay said to be of marine origin, but we saw no 

 fossils. It was an impalpable mud of brownish-green colour. 



Walking northwards from this place for a couple of miles, we came 

 to the hamlet of Mauri, and penetrating a wood found a most 

 interesting exposure (Fig. 3) of a rock called by Mr. Sederholm 



