phalen] the rocks of nugsuaks peninsula ^^5 



Even with the highest powers of the instrument, the determination 

 of the exact nature of these inckisions is unsatisfactory. The most 

 that may be said is that they are exceedingly irregular, often con- 

 tinuous and skeleton-like in shape. Of a dull brown color, they 

 must be composed essentially of iron oxide and are undoubtedly the 

 basis of the pink color of the feldspar. 



Such inclusions are often observed in the quartz, though when 

 present in this mineral, they are confined generally to the cracks 

 which seam this constituent. They have probably reached their 

 present position through capillary action, having originated in the 

 adjoining feldspathic minerals. Besides orthoclase, albite, and 

 microcline, there is still a fourth feldspar, which reveals a faint sug- 

 gestion of albite twinning. Owing to the imperfect development of 

 the twinning, and its extreme rarity, absolute measurements of its 

 extinction were well nigh impossible. Such as were made are very 

 small and the feldspar is undoubtedly the acid plagioclase, oligoclase. 

 The feldspars show a few inclusions of apatite, zircon, and sphene, 

 and at times rather large quartz grains. Rarely these latter show 

 a tendency toward micrographic development. 



Quartz is present in abundance, but only in its ordinary form. 

 The only colored constituent is biotite. It occurs in irregular scales, 

 never automorphic, rounded against the quartz and feldspar. At 

 times it is deep green in color, but more usually deep brown. The 

 greenish tints are peripheral and may be due to alteration. With 

 the biotite is associated much secondary magnetite, often in skeleton 

 crystals, often occurring in seams, and at times replacing its parent 

 mineral. Inclusions in the biotite could not readily be detected, owing 

 to the opacity of this mineral. Titanite, which is a notable accessory, 

 is frequently associated with the magnetite. Zircon and apatite, 

 which occur in small amounts, have already been mentioned. To 

 summarize, then, there are present albite, orthoclase, microcline, 

 oligoclase, quartz, biotite, kaolin, sericite, apatite, zircon, and sphene. 



An analysis of the rock follows : 



Analysis of Gneiss. (W. C. Phalen, Analyst.) 



SiOz 69.07 



AI2O3 14-09 



FeaOs 1.49 



FeO 2.37 



MgO 98 



CaO 3.14 



Na=0 5-i8 



K2O 2.71 



H2O above 100° 26 



