PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 829 



Greenstone and granite. Quartzyte.] 



Mic. This mineral is not pleochroic perceptibly, and has n f perpendicular to 

 the lamellae, which are numerous and not entirely parallel, some of them being hardly 

 transparent. It seems to be Muscovite altered from biotite, a condition of the dark 

 element of the granite. One section. 



Age. Archean (granite). N. H. w. 



No. 2046. GRANITE (with fluor). 



From Fluor island, in Saganaga lake, near the centre of sec. 14, T. 66-5. On the east side of the island, 

 south of the large quartz vein. 



Ref. Annual Report, xxiv, page 22. 



Meg. Bluefluorite is disseminated more or less in the mass of the granite, which 

 is red, some of the cubes being half an inch on the side. The cubic form does not, 

 however, generally appear. 



Mic. The section does not happen to cut any of the large fluorite grains, but a 

 few small irregular ones are visible. The rock in general is highly feldspathic and 

 contains hornblende and quartz. The feldspars have been much altered and recon- 

 structed by secondary feldspars, both in the form of zonal and of micropegmatitic 

 interpositions, and occasionally by microperthitic, accompanied by the development 

 of some microcline. Later a weathering decay has developed calcite and muscovite. 

 The small fluorite grains are of a faint amethystine color, and frequently are 

 included within the feldspars in specks and in spreading, spider-like forms. A few 

 grains of sphene are also in the feldspars. One section. 



Age. Archean (granite). N. H. w. 



No. 2047. GREENSTONE AND GRANITE. 



Greenstone ridge on the south side of West Sea Gull lake, N. W. 14 N. E. J4 sec. 17, T. 65-5 W. The green- 

 stone is cut by granite dikes. 



Ref. Annual Report, xxiv, page 23. See, also, Annual Report, xx, page 83, Nos. 648G to G50G. 



Meg. The hand sample shows the contact between the greenstone country rock 

 and the granite dike. The two rocks are firmly cemented. The greenstone is a 

 compact rock appearing like a fine-grained diabase. The granite is a white, fine- 

 grained aplyte, composed of quartz and feldspar with a very little biotite and 

 probably also muscovite. No section. 



Age. Lower Keewatin cut by granite. u. s. o. 



No. 2048. QUARTZYTE. ("Chalcedonic." j 



At the portage in sec. 12, T. 65-4, Saganaga lake. 



Ref. Annual Repqrt, xxiv, page 23 ; American Journal of Science, series 3, vol. xli, pages 386-390. 



Meg. So-called chalcedonic silica; appearance like that at Tower, embraced in 

 the granite. 



