phalen] the rocks of nugsuaks peninsula 191 



The texture is typically hypautomorphic granular, with porphyritic 

 structure, and when viewed through the microscope presents a most 

 heterogeneous appearance. This heterogeneity is in complete accord 

 with the macroscopic appearance of the rock, for in places it is 

 essentially syenitic, in other spots granitoid. Areas devoid of quartz 

 are contiguous to those where silica constitutes fully one-fourth the 

 mass. 



This silica does not have the appearance of typical original quartz ; 

 it does not form distinct crystals, but appears in vein-like masses, 

 elongated and irregularly shaped, surrounding large and distinct 

 microclines, and frequently enclosing smaller particles of the same 

 mineral. In this occurrence it is distinctly poecilitic. It has evi- 

 dently, at least in part, in these spots been produced as a result of 

 changes which the feldspar has undergone. To strengthen this 

 hypothesis, similar irregular masses, very much smaller than those 

 above referred to, occur in the midst of the larger feldspars. 



In addition to the secondary quartz, there is also present a smaller 

 portion of undoubted original quartz. This occurs with automorphic 

 outlines in sections from the prism zone with pyramidal terminations 

 and in various other irregular forms. Liquid inclusions are 

 abundant. 



Feldspar, of the variety microcline, constitutes the largest mass of 

 the rock. It is associated with a small amount of orthoclase. In the 

 former mineral a splendid development of the characteristic grating 

 structure obtains. This constituent, as well as the orthoclase, is uni- 

 versally filled with minute scales or lenticular particles of iron oxide, 

 at times segregated so as comparatively to obscure the mass of the 

 rock. These particles give, even in the thin sections, a faint reddish- 

 brown tinge to the rock and are the basis of the salmon pink color 

 observed in the hand specimen. These inclusions are frequently 

 massed, especially at the boundaries of the crystals and in those 

 portions of the rock where crystallization has taken place on a fine 

 scale, /. c, in the non-porphyritic portions. In the phenocrysts they 

 are scattered in irregular and broken lines and are accompanied by 

 a multitude of liquid inclusions. No perithitic intergrowths were 

 noted. 



Of accessories there are very few ; epidote and zircon were noted. 

 The former, of undoubted secondary origin, occurs in very irregular 

 patches, frequently elongated. It is faintly pleochroic and is much 

 obscured by segregated iron oxide. Basal cleavage is roughly de- 

 veloped. A scattering zircon was noted, but of apatite there is 

 apparently none. Allusion has already been made to the abundance 



