ELY GREENSTONE. 167 



imperfectly schistose, and may well be called amphibole- and mica- schists. 

 The rocks in this locality rejpresent one of the passage phases between the 

 normal greenstones on the one hand and the amphibole- and mica-schists 

 on the other, which, when close to the main mass of the g'rauite, show 

 none of the volcanic structures that enable their original character to be 

 easily determined here. This passage from the normal greenstones 

 through the amygdaloidal and ellipsoidal green schists to the normal schists 

 next to the granite can be seen still better just north of the quarter post 

 between sec. 19, T. 62 N., R. 12 W., and sec. 24, T. 62 N., R. 13 W., 

 and also along the quarter line in the southeast quarter of sec. 24, T. 62 

 N., R. 13 W. At this last locality we pass from the granite into an area 

 in wliich the schists and granites are most intricately mixed. The schists 

 occasionally still possess an imperfect amygdaloidal structure. To the 

 north we soon pass from very schistose greenstones to those which are 

 only slightly scliistose and in which amygdaloidal and ellipsoidal structures 

 are well developed. 



The ellipsoidal structure and the presence of spherulites, found most 

 frequently in association with these ellipsoids, have been referred to as 

 common features of the greenstones. Greenstones possessing both of these 

 characters occur very commonly in large exposures throughout sec. 10 

 and the west half of sec. 11, T. 63 N., R. 10 W. They can be very clearly 

 seen at a number of the exposures here, especially on one about 200 

 paces north and 1,000 paces west of the southeast corner of sec. 10, 

 T. 63 N., R. 10 W. Here the greenstone is separated into large ellipsoids 

 and the spherulites are arranged in concentric circles within the ellip- 

 soids. The smallest spherulites occur near the periphery of the ellipsoids; 

 the largest, 3 inches in diameter, occur nearer the center. These large 

 spherulites show their radial structure in sections on the weathered 

 surfaces of the rock. Some of them now consist of a chloritic mineral 

 having a dark-green color and a silky luster. In most cases they are 

 lighter colored, and the mineral constituting them is feldspar. The inter- 

 ference of the spherulites with one another in the process of growth is 

 very prettily shown in mau}' places. Very rarely are the}" perfectly 

 round. In most cases they have interfered with each other, and while in 

 some places nearly perfect spherulites may be observed, they are most 

 commonlv irregularly rounded and surrounded by others which have the 



