:'."')1 A. WINCHELL — RESULTS OF \ l;« 1 1 1 : \ n" STUDIES. 



have observed them, and they have a pretty uniform trend from northeast 

 to southwest. The mineral composition of the mass is similar to thai of the 

 masses jusl □ iticed, but the quartz element, while generally in abundance, 

 ■ I >es not develop individuals over a quarter of an inch in diameter. The 

 orthoclase on weathered surfaces is predominantly red, and exteusive areas 

 "ii Crooked lake fairly glow in the distance with a bio >d-red hue. The in- 

 dividuals Borne times attain a diameter of half an inch- In other places the 

 feldspathic element ceases to be granular and becomes a groundmass in which 

 - imetimes grains of quartz are imbedded, but more frequently, in this con- 

 dition of the feldspar, the quartz is absent or nearly so. The ferro-magnesian 

 element is mostly black hornblende to the east of Crooked lake, but westward 

 this is generally replaced by biotite, with occasional muscovite. A.cross a 

 zone of a quarter of a mile along the boundary the dark mineral is chloritic, 

 with little quartz, and Btains the feldspathic groundmass. In this vicinity 

 occurs a condition consisting of hornblende, menaccanite, and feldspar.* 



In a southwesterly direction the shores and islands of Burntside lake afford 

 striking examples of the nature of the formation and it- relation- to the 

 overlying crystalline schists, the bedded rock- retaining uniformly an attitude 

 nearly vertical. In this region hydromica gneiss frequently occurs, but 

 generally the dark mineral is either mica or born blend* 



A small oval, granitoid Area lies immediately west of Vermilion lake. 

 including the West hay, and might be styled the Vermilion Area. Its 

 longer axis is directed about N. 65 E., and it- length is ab »ut twelve miles. 

 The breadth of this A.rea is sis miles. The rock is mostly a biotite gm 

 It- ,-t rike is not persistently northeast and southwest, but concentric with 

 the border of the Area, and the dip is outward from the centre on all Bides, 

 gradually approaching a horizontal position at the centre. This is a very 

 significant departure from thai close adherence to a northeast strike observed 

 in the ol her and larger area 



From this region an expanse of mica schist extend- northwest aboul 50 

 milei Rainy lake, and this is followed by a belt of semi-crystalline Bchists 

 about live or sis miles wide, trending nearly N. 7> E. Beyond this we 

 find the Stanjikoming Arm of Lawson, inclosing all of the north-south arm 

 of Rainy lake,§ oblong in form, with it- longer axis N. 75 E., having a 

 length of 15 miles ami a width of '■'<-. The included area is occupied by 

 syenitic and biotitic gneisses with a border of crystalline schists and tb 

 remarkable included masses to which special reference will soon he made. 



md Iron •■. pp. 



III. 



RurnUid< see I p. Minn, G 1800, | 



injllcomln i, I 1 1 \ B 



i , Report on th logy of the Rainy Lake I II. 



