38 J. Stansfield — New Mode of Occurrence of Scapolite. 



approximately vertically, and strikes along the length of the 

 pit, i. e. N. 20° E. The northern end of the pit is occupied by 

 a rounded nose covered by a pegmatite vein. The pegmatite 

 has been broken through during mining operations, exposing 

 the gneiss below it. From the exposures now to be seen it 

 appears probable that the gneiss has been folded into a sharp 

 anticline. The pegmatite which was intruded at a later date 

 has taken on the form of an anticline, pitching to the south at 

 an angle of 35°, assuming a form which is comparable with 

 those of the saddle-reefs of Bendigo and of the " barrels " of 

 Nova Scotia. The pegmatite vein has a thickness of about 

 one foot and its upper surface is peculiarly smoothed. This 

 surface was in close contact with the graphite ore-body, the 

 ore being about one foot in thickness and being composed of 

 almost solid graphite at the contact with the pegmatite, becom- 

 ing poorer in graphite away from the pegmatite. With the 

 removal of the ore this smoothed surface has been laid bare, 

 showing an appearance very similar to the smoothed and 

 polished surfaces connected with glaciation. 



A thin section of the ore from the east face shows it to be 

 an altered Grenville limestone impregnated with graphite, and 

 shows the development of lime-bearing silicates as at the main 

 pit.* 



At the point where the pegmatite and altered limestone are 

 in contact the pegmatite is seen to be composed of quartz and 

 a greenish-yellow mineral, at first supposed to be a variety of 

 feldspar, but found on examination to be scapolite. This 

 scapolite-pegmatite is an integral part of the pegmatite vein, 

 and as such, is distinct from the altered limestone carrying the 

 graphite, and also carrying scapolite. The area of the scapo- 

 lite-pegmatite is but small, amounting to a few square feet only. 



Microscopic characters. — The rock is composed essentially 

 of quartz and scapolite. The relations of the two minerals to 

 each other are usually like those of a eutectic, and simulate 

 the olivine-anorthite typef rather than the orthoclase-quartz 

 type of eutectic relations. Occasionally, however, the scapolite 

 shows a tendency to the development of crystalline form. The 

 scapolite, then, crystallized in part before the quartz, in part 

 simultaneously with the quartz. The quartz shows strain 

 shadows and has inclusions of small particles of graphite. 

 Strings of gas bubbles are present and many very tine elon- 

 gated needles of an opaque mineral are numerous in the quartz, 

 being similar to those usually referred to rutile, though the 

 characteristic twinning of that mineral is not seen. 



The scapolite shows the uniaxial and negative character of that 

 mineral, and in basal sections the development of two cleav- 



* 12th International Geological Congress, Guide Book No. 3, p. 103. 

 f Geol. of Small Islands of Inverness-shire. Harker, 1908, p. 86. 



