318 THE CANADIAN NATURALIST. [Vol. viii. 



other minerals, but here and there a rude crystal may be observed. 

 The mica is present in small quantity, and is brown and strongly 

 dichroic. Magnetite (possibly titano-ferrite) is abundant, occur- 

 ing chiefly in irregularly shaped grains, but sometimes showing- 

 rude octahedral form. Sometimes it is seen in innumerable small 

 grains imbedded in the auuite. The viridite is abundant and 

 very bright green. It occurs largely in fibrous or sheaf-like ag- 

 gregations showing faint dichroism, and with the polariscope 

 changing, on rotation of the analyser, from blue to brown. In all 

 probability it is chlorite. The apatite is found in sharply denned 

 acicular crystals which are hexagonal when seen in cross section. 

 It is most abundant in the feldspar, but is also seen to penetrate 

 the mica, augite, and even the magnetite. 



II. Granville, Lot 9, Range V. When examined with the 

 microscope the section of this rock is, like that last described, 

 seen to consist of plagioclase, augite, magnetite, viridite, pyrite 

 and apatite ? The feldspar forms a network of blades, and has 

 in places undergone some alteration, although for the most part 

 it appears to be unaltered and with the polariscope becomes 

 beautifully banded. It is distinctly seen to penetrate the mag- 

 netite in a number of instances, and must therefore have solidified 

 before, or at least simultaneously with the magnetite. It also 

 contains a good many of what appear to be glass- and stone- 

 cavities. The augite is brownish-grey in colour, traversed by 

 numerous fissures and penetrated in all directions by blades of 

 feldspar. The rock contains a good deal of magnetite, mostly 

 in grains of irregular form, but occasionally in octahedral crys- 

 tals. When cut across the grains are often seen to contain 

 numerous irregular cavities, and in one case an octahedral crystal 

 was observed which was hollow, or nothing more than a shell. 

 Viridite is present in considerable quantity. It is much duller 

 green than that in the rock last described, and looks more like an 

 alteration product of the augite. It is mostly amorphous, but 

 occasionally occurs in sheaf-like aggregates. Pyrites is present in 

 small irregular grains scattered here and there through the rock.^ 



* Specimens I and II were many years ago analysed by Dr .Hunt, 

 who described them as follows : u The dykes of this most ancient 

 dolerite or greenstone in Grenville have a well-marked columnar 

 structure at right angles to the plane of the dyke. They are fine- 

 grained, dark greenish-gray in color, and weather grayish-white. 



