Petrographical Relations of Laurentian Limestones. 11 



Foliated Granite, Township of Glamorgan, Range IX., 

 Lot 9. {Section 1273.) 



This rock is pinkish and usually fine-grained, with 

 occasional good sized individuals of feldspar. It has a 

 banded structure which is quite distinct, the darker con- 

 stituents occurring almost entirely in fairly continuous, 

 narrow ribbons, to which, moreover, the arrangement of 

 the grains is parallel ; this indicates a foliated structure 

 also. The more acid bands have a greater width — an 

 inch or more — and in them also, the dark constituents, 

 wherever they do occur, are arranged with their long 

 axes parallel to the banding. 



Under the microscope it is seen to consist essentially 

 of quartz, plagioclase, microcline, with some orthoclase, 

 and biotite. Muscovite, numerous grains of magnetite, 

 sometimes enclosing pyrite, and a few little crystals of 

 zircon and of apatite also occur. 



The quartz is in clear glassy grains, both large and 

 small, and of irregular form. It is often cracked, and in 

 other individuals shows well marked undulose extinction 

 or strain-shadows. The orthoclase, which is somewhat 

 turbid, is recognized by its being twinned according to 

 the Carlsoad law, though this twinning is not always 

 seen. It frequently shows slight strain-shadows, and it is 

 without doubt from a straining of the orthoclase that the 

 microcline has been derived. This seems especially prob- 

 able, for in this rock both these minerals are pink in 

 color. The microcline is comparatively fresh, and is 

 distinguished by its characteristic cross-hatched appear- 

 ance in polarized light. The plagioclase is generally in 

 large individuals, and frequently turbid ; it is oligoclase 

 Both the orthoclase and the plagioclase occasionally show 

 cleavage. The biotite is not present in large amount. It 

 is in narrow, lath-shaped individuals, brown, with some- 

 times a greenish tinge, and quite strongly pleochroic ; 

 cleavage well shown. The muscovite, which also often 



