GEOLOGY OF THE SCHROON LAKE QUADRANGLE I3 



Olmstedville-Irishtown area. This area of Grenville is almost 

 certainly connected, under the Pleistocene of Minerva stream val- 

 ley, with the Minerva area. 



In Olmstedville, by the stream one-fifth of a mile east of the mill, 

 there is a big ledge of typical limestone. At the bridge just east 

 of Olmstedville, limestone underlying hornblende gneiss forms a 

 ledge 100 feet long. By and near the road one-third of a mile 

 east of the bridge just mentioned, there are several outcrops, includ- 

 ing hornblende gneiss, rusty mica quartzitic gneiss and limestone. 



Two small outcrops of limestone occur by the road about a mile 

 east of Olmstedville. 



In a field i^ miles northeast of Olmstedville, there is a large 

 exposure of typical graphitic limestone with some small masses 

 of rusty gneiss twisted into it. Nearby is an outcrop of horn- 

 blende gneiss. 



Near the road one-half and three-fourths of a mile, respectively, 

 southwest of the village, there are several small exposures of 

 graphitic limestone with some small masses of closely involved 

 pyroxene gneiss. The one nearest the village is weathered to a 

 friable mass and is used for repairing roads. 



Near the road corners one-half of a mile northwest of Olmsted- 

 ville there are several outcrops of limestone, some containing 

 graphite and green pyroxene and associated with hornblende gneiss. 

 From this locality northward for a mile, by and near the road, 

 there are other good exposures of similar rocks. 



From one-half to i mile east-southeast of Irishtown there are 

 interesting exposures of Grenville. Coming against the syenite 

 on the south side (see map) there are several good exposures of 

 limestone arranged along a strike N 70° W. Just within the syenite 

 there is a long, narrow inclusion of quartzite. Where the limestone 

 belt comes to the road, hornblende gneiss outcrops. Just north 

 of the tongue of syenite there are large exposures of quartzite with 

 a little associated limestone arranged along a N 70° W strike. 



One mile north-northwest of Olmstedville, and extending from 

 the road eastward for 200 yards, there are good outcrops of rusty 

 biotite gneiss, hornblende gneiss and quartzite. 



Along the road from one-half to i mile north of Irishtown, there 

 are several exposures of hornblende gneiss (some garnetiferous) 

 and a little associated limestone. 



The tongue of Grenville which forms part of the mountain spur 

 I mile north-northeast of Irishtown consists of hornblende and 



