200 



Mr. S. Allport and Prof. T. G. Bonney. [June 6, 



found to be of Archaean age, and of which the origin is still doubtful, 

 than of a normal mica-schist. They exhibit that peculiar purplish- 

 brown or purplish-grey tint which is so common in the quartz-mica 

 rocks resulting from contact metamorphism, and is doubtless due to 

 the peculiar tint of the micaceous constituent. 



Of the first three specimens, 406, 407, 408,* taken from the same 

 locality, about 12 yards from the granite, we need only remark that 

 one exhibits, macroscopically and microscopically, a slight mineral 

 bandiug, indicated by variations in the proportions of the quartz, 

 mica, and a brownish earthy-looking dust, which are the chief con- 

 stituents of the rock. To this banding the flakes of mica tend to lie 

 roughly at right angles. In the other two specimens, fragments of 

 quartz and of altered felspar can be detected. In one the latter is 

 abundant, and the frequency of an earthy dust, and of a mixture of 

 microcrystalline quartz with tiny flakelets of mica or a kaolinitic 

 mineral, renders it probable that the original rock was a rather 

 felspathic grit. A vein of calcite is present in the slide. The other 

 specimen possibly contains a little andalnsite. 



The next specimen (409) exhibits fragments rather distinctly, some 

 being about 0"05" in diameter. In those of felspar traces of twinning 

 can be detected, showing the mineral to be either a plagioclase 

 twinned on the pericline type or a microcline. The matrix is more 

 free from " dust " than in the former specimens, so that the rock has 

 a more distinctly hoi ocry stall ine aspect. A few grains of epidote are 

 probably present. 



The next two specimens (410, 411) were collected about 40 yards 

 from the nearest visible granite. Both assume a tinge of green in 

 weathering. One differs little from some of those already described ; 

 the other is macroscopically rather distinctly " spotted ; " both exhibit 

 light specks such as might indicate a felspar, and elongated darkish 

 spots or streaks lying roughly parallel. Hornblende is rather abun- 

 dant, associated with or replacing the brown mica; also a few grains 

 of pyrite. There are fragments as above described, one or two 

 reaching 0' 04' ' in diameter; the presence also of rock fragments is 

 suggested, but the evidence is inconclusive. From the condition of 

 the matrix one would infer a rather earthy condition for the original 

 grit. 



The next specimen (414) is from a junction, and a vein of light 

 coloured, finely granular, non-micaceous granite, about 1^-" thick, is 

 present in the hand specimen. The altered rock is rather more 

 coarsely crystalline in aspect than the others, white mica is present 

 in fair-sized flakes, and there are many irregular blackish spots, like 

 stains, about 0"14" diameter. Microscopic examination shows that a 

 fragmental structure is still marked, and that bits of rock are present. 

 * These numbers are painted on the specimens. 



