690 THE GEOLOGY OF MINNESOTA. 



[Granite. Hornblende schist. Dioryte. 



Meg. Diabase, having conspicuous feldspar crystals of porphyritic habit. 



Mic. The section shows none of the large feldspars. It is in all respects similar 

 to No. 1312, except that the elements are all coarser, and that through alteration 

 much ftctinolitc has been developed. One section. 



Age. Sill in the Animikie. N. H. w. 



No. 1316. GRANITE. 



North side of Black Fly bay, at the outlet of Gunflint lake. 



Ref. Annual Report, xvi, pages 73, 121 ; Annual Report, xvii, pages 199, 203. 



Meg. Gneissic. 



Mic. Much decayed, the feldspars being rendered almost non-transparent. 

 Contains quartz, some pennine, sphene and probably orthoclase and oliyoclase. One 

 (thick) section. 



Age. Archean. N. H. w. 



No. 1317. HORNBLENDE SCHIST. 



Enclosed in No. 1316. 



Ref. Annual Report, xvi, page 121. 



Meg. A rather fine-grained rock, composed of hornblende and feldspar with a 

 few large grains of quartz. No section. 



Age. Archean. u. s. G. 



No. 1318. DIORYTE. ( Camptonyte? ) 



At the first falls going north from the outlet of Gunflint lake. 

 Ref. Annual Report, xvi, page 121 ; Annual Report, xvii, page 199. 



Meg. Darker portion of the gneiss, spreading irregularly, but in manner of a dike. 



Mic. The rock is colored by hornblende, which is in distinct, well-cleaved crys- 

 tals, as well as in form of an alteration product which is less doubly refractive, almost 

 non-pleochroic and has an imperfect short fracture-cleavage parallel or nearly 

 parallel with which extinction takes place, and is in general a fibro-scaly, dull-green 

 substance which seems to agree physically with the descriptions of itralite. Fresh 

 adinolite (or griinerite?) fibres pass through this substance, showing a fine twinning. 

 This uralitic substance has n v for acute bisectrix. 



Epidote in considerable quantity is also present. The original feldspars are much 

 altered and are indeterminable. They are rejuvenated by secondary growths which 

 are fresh, and which are distributed irregularly through the old grains, and about their 

 borders. With pennine in small amount, and some calcite and quartz. One section. 



Age. Archean. 



Remark. This rock is the same as No. 61G, described on pages 160, 161, Seven- 

 teenth Annual Report It is in form of a dike, and cuts both granite and schist. 



N. H. W. 



