phalen] the rocks of nugsuaks peninsula 203 



etc. In places it shows undulatory extinction. It appears to be de- 

 composed in spots throughout ; the ferromagnesian constituents have 

 completely changed and the feldspar has suffered locally in the same 

 way, while in places the latter mineral is remarkably fresh and 

 determinations of its character may be made with ease. The posi- 

 tions of the pyroxene and olivine, if the latter mineral were ever 

 present, are now occupied by green and brown pigments. Mag- 

 netite, of course, is always present. 



The constituents may be described as follows : Feldspar, the most 

 abundant of the components still preserved in fresh condition, shows 

 abundant albite and Carlsbad twinning. Symmetrical extinctions 

 on the trace of the clino-pinacoid (010) range as high as 35.6°. 

 The Michel-Levy method of Carlsbad and albite twins corresponds 

 to a plagioclase of the composition AbgAn^, which is borne out by 

 the high symmetrical extinction given above. Thus the plagioclase 

 may be termed a labradorite bytownite and is very basic in composi- 

 tion. 



In spots this feldspar is much kaolinized ; it is cracked and 

 secondary calcite has filtered into or formed in the fissures, filling 

 them completely. Flakes of the greenish pigment to be subsequently 

 described are also present, as well as elongated, lenticular, and lath- 

 shaped forms of the same coloring substance. In general these in- 

 clusions are without regular orientation, but in the vicinity of and 

 along the composition planes, there is a parallelism evident. At 

 times cloud-like masses, elongated normal to the C axis, were de- 

 tected with the number 7 objective. Magnetite, though an inclusion, 

 is not abundant in the plagioclase. Its form is not automorphic, 

 and part, even here, may be secondary. 



The residual mass of the rock is largely a conglomerate of de- 

 composition products, of which the most abundant are iron ore, cal- 

 cite, chlorite, and serpentine, and much material, isotropic and sec- 

 ondary, whose properties are not at all diagnostic. These minerals 

 are scattered promiscuously throughout the rock, in contact with 

 and overlying each other. If we assume that the calcite areas rep- 

 resent original pyroxene and the serpentine is taken as a rough 

 index of former olivine, then the original rock consisted of pyroxene, 

 feldspar, olivine, magnetite, and apatite, in the order given. 



From the intervening localities, at which explorations were con- 

 ducted, namely Saviarkat, Kookangnertunek, and Niakornat on the 

 north side of the peninsula, and Ata and Patoot on the south side, 

 nothing of petrographic interest was obtained, owing to the very 

 advanced state of decomposition of the rocks at these places. At 



