phalen] the rocks of nugsuaks peninsula ^97 



abundantly in the prochlorite occur magnetite and hematite, without 

 definite form, appearing in irregular scales, sometimes occupying 

 entire centers of chlorite masses, at other times arranged peripherally 

 in tiny elongated and jagged masses, normal to and in contact with 

 altering olivine surfaces, as already noted under that mineral. Iron 

 ore is also included in the chlorite, resulting from pyroxenic altera- 

 tion. What appears to be iron ore is also relatively abundant in 

 both the radial and parallel systems of cracks. That it is not mica 

 is proved by its non-pleochroic character and from the fact that it is 

 almost universally confined to the ferromagnesian constituents, end- 

 ing abruptly at their junctions with the plagioclase. In color it is 

 light reddish-brown, and this ends its resemblance to the small 

 amount of biotite occiirring in the rock. It is filled with flakes of 

 black iron oxide, which seem to have resulted from it, and is with- 

 out doubt limonite, partially changed in spots to magnetite and 

 hematite. 



The remaining constituents of the rock are biotite, feldspar, apa- 

 tite, with small amounts of chromite and pleonaste. The biotite is 

 dichroic in dark and light shades of brown, the latter tint becoming 

 very nearly colorless. Owing to the trifling amount of feldspar 

 present, enough satisfactory measurements could not be made to 

 judge of its exact composition with any degree of assurance. It 

 exhibits albite twinning wherever it occurs, but symmetrical extinc- 

 tions were more difficult to obtain. The highest equal extinctions 

 were 25.5°, indicating a feldspar of composition approximating 

 AbiAn^. 



Apatite occurs in relatively large amounts in the usual form of 

 long, slender prisms in radiating aggregates. A small amount of 

 chromite with a trifling amount of pleonaste were also detected by 

 chemical means. 



An analysis of the pyroxene follows : 



SiO. 49-49 



AI2O3 5-45 



FesOa 1.04 



FeO 3-39 



MgO 15-88 



CaO 24.07 



NasO 82 



MnO .18 



100.32 



Sp. Gr 2.890 . 



