PETROGRAPHIC GEOLOOY AND DESCRIPTIONS. 537 



(i;ittlro. Anorthosj'to.] 



plates. Move complete descriptions of this type of rock are given under some of the 

 following numbers: 960, 962, 1041, 1336, 1338, 1349, 1340, 1343, 1362. 



One poor section examined. 



Age. Iron-bearing member of the Animikie(?) u. s. G. 



Remark. It has been found later that this ferruginous qiiartzyte, and a number 

 of other localities of the same kind further southward, formerly referred to the 

 Animikie, probably are portions of the Keewatin, affected by the gabbro. N. n. w. 



No. 769. GABBRO. 



Northwest end of Little Saganaga lake; perhaps from S. E. % S. E. % sec. 6, T. 64-5 W. 

 Ref. Annual Report, x, page 98; Bulletin ii, page 7'2. 



Meg, A medium-grained, gray, granitoid rock, composed of plagioclase, augite, 

 hornblende and magnetite, with a little biotite and apparently someolivine, although 

 this mineral is not seen in the section. A part of the great gabbro mass. 



Mic. M. E. Wadsworth's description of this rock is as follows:* 



"Is a brownish-gray coarsely crystalline rock, like the preceding. In the thin 

 section the rock is seen to be somewhat altered, while it has its plagioclase filled with 

 the brownish needles and globuliths so commonly seen in the feldspars of gabbros. 

 These, as usual, are arranged alpng cleavage planes, one well marked arrangement 

 being parallel to the polysynthetic twinning planes, although one crystal was observed 

 in which no microliths were seen, whose position corresponded to the striation lines, 

 but all cut these lines at a small angle." 



One poor section examined. 



Aye. Cabotian. u. s. o. 



No. 770. ANOKTHOSYTE. 



South side of Little Saganaga lake; N. W. % sec. 10, T. 64-5 W. 

 Ref. Annual Report, x, page 98. 



Mey. A medium-grained, gray rock, composed almost entirely of plagioclase, 

 weathering nearly white. 



M/'e. The section is a granitoid aggregate of p/ay/or/ase. With the possible 

 exception of a few small grains of >no(/netite the section shows no evidence of any 

 original mineral other than the plagioclase, which is in places kaolinized. A few 

 small fli /in' i fe scales are present. The plagioclase is commonly twinned according to 

 the albite law. Approximately equal extinctions run up to 30. Two grains cut 

 approximately normal to the least axis of elasticity gave extinction angles of 40 

 and 44; sections parallel to 001 gave 16 and 17; and sections parallel to 010 gave 

 30 and 31. The plagioclase thus appears to be bi/toin/ifc. One section examined. 



Aye. Cabotian. r. s. G. 



'Bulletin ii, p. T:.'. 



