194 R. Workman — Calcite as a Primary Constituent 



as it were, by a fringing archipelago known as the 'skargard', and 

 the distinctive feature of the numberless lowly islets included in this 

 skargard is a complete absence of soil and vegetation. Every here 

 and there, bare, smooth, and rounded, granite and gneiss rise out of 

 the sea to a fairly uniform level, beautifully polished and striated — 

 a truly remarkable memorial of the former presence of a great ice- 

 sheet. Only a few Scotch firs have been able to root themselves 

 in cracks and crevices, and except for an occasional coastguard station 

 the solitude is complete. In the midst of this strangely attractive 

 barrenness appears a beautiful fertile oasis, covered with trees, fine 

 meadows, cornfields and prosperous homesteads. It is a merry and 

 hospitable people that has cultivated and developed this little patch, 

 and we have cause gratefully to remember the genial farmers who 

 came forward to welcome us and put at our disposal all the fruits of 

 the earth with the utmost goodwill. They gladly threw open their 

 fields and exposed their property to the searching gaze of the 

 geologist and to the destructive denudation caused by many active 

 hammerers. 



One instinctively wonders what produces this remarkable change of 

 scene. It is, in fact, nothing else than the little complex of alkali 

 igneous rocks, responsible for the present paper. The boundary of the 

 oasis is precisely the boundary of this alkali igneous complex, and as 

 one passes outward in all directions on to the surrounding gneiss and 

 granites the landscape again resumes its wonted barrenness. 



Primary calcite plays a very important part in the complex under 

 consideration. It is present in all proportions, occasionally forming 

 the main bulk of the rock. Alike in the field and under the micro- 

 scope it presents all the appearances of a truly igneous constituent. 

 It is found in rocks of every type varying between nepheline-syenite 

 and coarse-grained, banded limestone, in all of them intercrystallized 

 with undecomposed segirine, nepheline, and other typically igneous 

 minerals. In places, too, it forms calcite pegmatites, showing 

 excellent graphic intergrowth with olivine, mica, and iron ores. It 

 also occurs in fine-grained limestone dykes, cutting both the nepheline- 

 syenite and the coarsely crystalline banded limestones, and bounded 

 by chilled margins against these rocks. 



At the edge of the complex where the intrusion comes in contact 

 with the gneiss there are clear indications of marginal assimilation. 

 Quartz appears in the intrusion, no doubt derived from the country rock. 



In describing some of the rock-types I will adopt the following 

 order : — 



1. The Country Rock. 



2. The Plutonic Pocks, including the Massive Limestone. 

 8. The Dyke Rocks. 



1. The Country Rock. 



Little need be said of the Country Rock except that it is a coarse, 

 grey, Archaean gneiss, rich in biotite, felspars and quartz. In the 

 neighbourhood of the plutonic intrusion a curious baked variety of 



