428 MB. E. M. ANDERSON ON THE GEOLOGY OF [vol. lxxix, 



A very fine-grained pelitic rock is associated with the Grey 

 Schist in one or two localities. It consists for the greater part of 

 quartz, muscovite, and biotite, in minute grains and flakes, or of 

 quartz and biotite with a certain amount of orthoclase. It is, how- 

 ever, partly calcareous, and one slide with calcific laminse shows 

 fairly abundant scapolite. Carbonaceous material appears to be 

 confined to the calcareous portions. 



Grey Limestone and White Limestone. — These two, 

 although separated by the Banded Series, are treated together for 

 comparison. They are both coarseby crystalline non-dolomitic 

 marbles. The former is the more massive, and, on the whole, the 

 more purely calcareous type. A microslide of the Grey Limestone 

 shows a matrix of large grains of calcite, enclosing some flakes of 

 muscovite. There is an entire absence of any magnesian mica. 

 The calcite contains a certain quantity of fine-grained carbonaceous 

 material similar to that found in the Grey Schist. Two slides of 

 the White Limestone both show magnesian mica, and one has 

 finely-developed tremolite, which is well seen in the hand-specimen. 

 In neither case is there carbonaceous material. These distinctions 

 correspond more or less with the differences observed in the field. 

 The Grey Limestone is tj^pically dark when unweathered; and 

 the weathered material, though lighter, has usually a perceptible 

 greyish tint. The White Limestone is lighter when unweathered, 

 and has a characteristic creamy weathering. The brownish mag- 

 nesian mica seen in the slides is a very common constituent. 

 Samples of Grey Limestone dissolved in hydrochloric acid leave a 

 residue which is partly black, with the property of marking paper, 

 while this type of material is absent from White Limestone residues. 

 It is, therefore, fairly clear that the Grey Limestone owes its colour 

 to the presence of carbon. 



Banded Series. — This division was taken by Mr. Wilson to be 

 a ' sheared ' part of the Quartzite. It contains at least one rather 

 massive band of quartzite, but consists for the greater part of very 

 rapid alternations of siliceous and micaceous rock. The two types 

 are sharply contrasted in colour, owing to the large amount of 

 biotite in the micaceous layers. Often several bands of each type 

 are crossed in the distance of a foot. 



There is a tendency to rusty weathering in this series, and it is 

 only with difficulty that fresh material can be obtained. A slide 

 cut from a siliceous band shows a mosaic consisting of about 75 

 per cent, of quartz-grains, and 25 per cent, of felspar. The latter 

 is altering into some flaky material, and the individual quartz- 

 grains are surrounded by films of limonite. A slide cut from a 

 micaceous band shows abundant flakes of dark biotite, set in a 

 matrix like the rock just described. The felspar is however 

 unaltered, and, though untwinned, is either oligoclase or andesine. 

 Muscovite is entirely absent. 



