144 ^'^ Afnerican Geologist. September, l89^ 
and red earthy iron oxides, which are often sufficient to give 
the rock a brick red apeparance. The prevalent color is dark 
brown. The feldspars surrounding the altered olivine are 
always filled with fractures arranged radially around the oli- 
vine. According to Prof. Judd, this shattering of the feld- 
spar is produced by the hydration of the olivine, during which 
process, on account of the increase in the bulk of the mineral, 
there is an expansion on this part of the rock, and a fractur- 
ing of the unaltered minerals around the olivine.''^ 
Noryte. Hypersthene is frequently present as an accessory- 
mineral in the gabbro mass. It sometimes predominates over 
the other pyroxenes and olivine, even being the only ferro- 
magnesian mineral present. The rock then becomes a noryte. 
Around West Greenwood lake in T. 58 N. R. 10 W. this rock 
is extensively developed. It is coarse grained and unaltered. 
The color is light gray with brown spots evenly distributed. 
The texture is granitic. The noryte occurs quite extensively 
along the northern border of the gabbro, where it was recently 
described by Bayley (41, vol. III., pp. 1-20). The texture of 
the rock there is granulitic and is regarded as a phase of the 
gabbro due to contact phenomena. In section 21, T. 63 N. R. 
4 W. and in the region west of Brule lake there is also an ex- 
tensive development of the granulitic noryte. This rock is 
fine grained and usually has a darker color than the normal 
phase of the rock. In the last named localities it is intimately 
associated with the magnetite deposits of that vicinity. 
AnortJiosyte . This is ccmposed essentially of plagioclase 
with the other mineral constituents as accessory. The usual 
proportion being 90 to 95 per cent of plagioclase and 10 to 5 
per cent of pyroxene, olivine, magnetite, etc. This rock is 
apparent in the central part of the gabbro area, and it has 
been noticed especially south and west of Little Saganaga 
lake, T. 64 N., R. 5 W., and for fifty miles westward of that 
locality as far as the gabbro remains uncovered. The anor- 
thosyte has a white color and usually stands out quite promi- 
nently from the other phases of the gabbro. 
Pyroxenyte. When the rock is composed entirely of the 
pyroxene minerals it is dark in color and much heavier than 
*Quart. Jour. Geol. Soc. London, 1886, No. 165, vol. XLII, p. 86. 
