380 THE GEOLOGY OF MINNESOTA. 



[Diabase. Graywacke. 



Remark. In general the rock has the same composition as other graywackes 

 from this region. It seems to represent debris from a granitic rock mixed with some 

 finer material most of which has crystallized as chlorite and sericite. u. s. G. 



No. 474. DIABASE (with olivine). 



Dike rock near Carlton. There are several similar dikes in the near vicinity. This one is thirty feet 

 wide. The slates dip 57 to the S. 5 E. (compass). The dikes all run about N. 5 E., with a slight variation 

 either to the east or west of that, which is about the direction of the main gabbro mass northward from Rice's 

 point. 



Ref. Annual Report, x, page 18. 



Meg. The rock is not distinguishable from that of the dike, already mentioned, 

 running north and south under the railroad bridge near Thomson. 



Mic. The feldspar shows extinction on 010 at 24, indicating labradorite-bytownite. 

 The olivine is sometimes changed to botrlingite. Biotite is shown by its pleochroism 

 and chlorite by its green color. These with augite and magnetite constitute the rock. 



Two sections. 



Age. (Cabotian?) dike in the Animikie(?) N. H. w. 



No. 475. DIABASE (with olivine). 



From the most westerly of several dikes at Carlton. This dike passes west of Paine's sawmill. 

 Ref. Annual Report, x, pages 18, 27, 29. 



Meg. This dike differs from the foregoing in having conspicuous porphyritic 

 feldspars. One of these cut perpendicular to n e has extinction at 23, which is 

 indicative of labradorite. Another parallel to 010 has extinction at 19. 



There are small augites which preceded the feldspars, but in the main the augite 

 is later than the feldspar and embraces it ophitically. Apatite and magmiitr are 

 common/but olivine is not evident, as it is obscured by accumulations of magnetite. 



One section. 



Age. Cabotian dike in Animikie(?) N. H. w. 



No. 476. GRAYWACKE. 



From the south bank of St. Louis river, about a mile above Knife falls. 

 Ref. Annual Report, x, pages 20, 21. 



Meg. Rather fine and granular, gray, coarsely schistose. 

 Mic. This rock appears like Nos. 469 and 465. 

 One section. 



Age. Keewatin(?) N. H. w. 



No. 477. GRAYWACKE. 



Same locality as No. 20. 



Ref. Annual Report, x, pages 20, 21. 



Meg. A gray rock composed of small quartz and feldspar grains in a finer 

 grained background. 



