352 C. W. HALL — KEEWATIN OF EASTERN AND CENTRAL MINNESOTA 



The dike is badly weathered. Its texture is medium, and comj)osi- 

 tion appears uniform : a basaltic structure is in the fresher portions, and 

 a decidedly concentric weathering where greatest alteration is shown. 



MOOSE LAKE EXPOSURES 



Moose lake affords an exposure or two of some interest. Near the saw- 

 mills a railroad cat has been made to the deptli of several feet in the 

 clean gray schists. There is variation in texture from a mediumly 

 coarse yet well defined schist to a slaty variety greei:4ish gray in color 

 and glossy in habit, yet lacking slaty cleavage. Bands of a few inches 

 in thickness, consisting of calcium carbonate, occur in these glossy 

 foliated rocks. The strike is north 70 degrees east, dip varying from 

 to 25 degrees toward the south 20 degrees east. Some contortion was 

 noted. A dike of diabase porphyrite occurs in the west part of the 

 town, cutting through the schists without modifying their rock-hal)it to 

 any perceptible extent. 



Kettle River Section 



From section 21, townshij) 46, range 20 west, to section 36, township 

 45, range 20, a distance of 10 miles, there is a most interesting series of 

 exposures of hornblende-biotite schists. The rocks are very uniform in 

 their structural characters and external lithologic habit. Layers of a 

 decidedl}^ quartzose habit alternate with the normal schist. With these 

 are, more rarel}'', bands of a carbonate. At the northernmost exposure in 

 section 21, township 46, range 20, there is exposed a wide vein of quartz 

 regarded as the southwestward extension of the one outcropping in the 

 Saint Louis river at Thomson and already mentioned. A mile and a 

 half below this exposure the schists which lie in both banks of the river 

 for a considerable distance are badly shattered and badly altered, so 

 much so that they have been mapped by the Minnesota survey as Cam- 

 brian sandstone.* The strike of these rocks is very nearly east and 

 west, varying perhaps to north 80 degrees to 85 degrees east, with a 

 southerly dip, varying from 15 to 30 degrees. 



Onl}'' half a mile from the locality just noted is an exposure 20 feet or 

 more above the river, containing a notable per cent of grai)hite. It is 

 situated 100 paces from the river ; direction of strike, north 60 degrees 

 east, magnetic, dipping south 30 degrees east, at an angle varying from 

 3 to 30 degrees. While the exposed area is not great, the indications 

 in the black soil, widely distributed graphite chips and attitude of 



*Geol. and Nat. Hist. Survey of Minnesota, final report, vol. iv, 1899, pi. 5G. 



