from Krageroe, Norway. 



511 



which at times exhibits slight alteration to leucoxene, is 

 associated with the rutile. A single small grain of pyrite was 

 observed inclosed in one of rutile. Apparently the rutile does 

 not show predilection for one rock mineral more than for 

 another. It occurs entirely enveloped by feldspar, along the 

 sutures of feldspar individuals and of feldspar and quartz, and 

 sometimes penetrates into the substance of both. The rela- 

 tions of the rutile to the silicate rock minerals suggest that it 

 crystallized from the magma as did the feldspar and quartz, 



Fig. 1. 



Fig. 1. Microphotograph of kragerite, a rutile-bearing aplite, from 

 Krageroe, Norway. The black grains and crystals are rutile ; other con- 

 stituent is chiefly sodic feldspar. Nicols crossed. Magnified 27 diameters. 



and that the usual order of crystallization Avas observed. 

 These relations are shown in fig. 1, a microphotograph of a thin 

 section of the rock. 



A thin section of the rutile-rich portion of the rock, repre- 

 senting probably the schlieren of Professor Brogger, was 

 studied microscopically. It was composed chiefly of rutile, 

 together with some biotite, partly altered to chlorite, a few 

 anhedral grains of apatite, and an altered light-colored silicate 

 mineral, probably a potash feldspar. 



In reflected light the rutile is dark brown to gray with the 

 faintest greenish tinge; in transmitted light it is pleochroic, 



