GEOLOGY OF THE VICINITY OF LITTLE FALLS 91 



result proving that the ore is not titaniferous to any appreciable 

 extent, the figures being certainly under .5^. 



The inclusions are of apatite, augite and quartz. The two 

 former are numerous, though rather small, have good idiomorphic 

 boundaries against the magnetite, specially in the case of the 

 apatite, which clearly formed before the magnetite, as did appa- 

 rently some of the smaller augites also. The augite is of pale 

 green color, without pleochroism, exactly like that of the wall 

 rock. 



The quartz inclusions are of much interest. They are of the 

 elongated leaf or spindle shape, like the quartz of the inclosing 

 gneisses, and some of them are of large size. Polarized light 

 shows that they are composed of a much greater number of sepa- 

 rate mineral fragments than usual, and all show strong undula- 

 tory extinction. Around many of them is a zone, or rim, of finely 

 crystalline augite. These rims are also duplicated in some of the 

 inclosing gneisses and seem clearly due to reaction between the 

 magnetite and quartz. In the gneisses they only form between 

 magnetite and quartz. They are exceedingly like the augite rims 

 which form about quartz inclosures in basic igneous rocks. Why 

 they do not occur about all the quartzes is a puzzle. The writer is 

 disposed to regard the presence of the quartz in the ore as due to 

 metamorphism and attendant recrystallization, whence it would 

 follow that the rims formed as a result of the same process. 



Walls. Inclosing the ore, and grading into it, is a very basic 

 gneiss composed of hornblende, magnetite, augite, feldspar and 

 quartz, the black minerals constituting 75^ of the rock. Horn- 

 blende is much the most abundant of these. About equal amounts 

 of quartz and feldspar are present, the feldspar being part oligo- 

 clase and part anorthoclase. 



So far as can be judged from specimens obtained from the 

 dumps, this gneiss grades rapidly into a more feldspathic horn- 

 blende gneiss, and the latter into a syenite gneiss, at first basic 

 but rapidly becoming more acid. 



The more basic rock shows abundance of fairly coarse hyper- 

 sthene, which is platy, lies in the foliation planes, gives the rock a 



