GEOLOGY OF THE LONG LAKE QUADRANGLE 



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A slightly different, though yet more silicious rock is a quartz 

 gneiss from the small Grenville area lying between Long lake and 

 Pickwacket pond. It is a quartz, feldspar, phlogopite rock, with 

 zircon as the only observed accessory mineral. The feldspar is so 

 altered as to unfit the rock for chemical analysis, but still admits of 

 accurate microscopic determination. Part of it is oligoclase, about 

 J\b 2 An x , and the remainder seems orthoclase, at least it is un- 

 twinned. With no analysis of the phlogopite available it is as- 

 sumed to have the composition of the phlogopite from Edwards, 

 N. Y. 1 With these assumptions the microscopic analysis yields the 

 following result (2-H-1). 



Units 

 Units measured Sp. Gr. by weight % weight 



Quartz 2060 x 2 . 65 = 



Feldspar 326x2.64 = 



Phlogopite 198 x 2 . 85 = 



Zircon . . . 

 Total. 



5459 



= 



79- 1 3 



861 



= 



12. 48 



564 



= 



8.18 



3^4-5 = 



25S7 



14 





Qz. 



Alb. 



Anor. 



Phlog. 



Zir. 



Total 



Si0 2 



79-J3 



6.48 

 1.80 



1.08 



1.34 



1 . 12 



0.66 

 







3-9 1 

 o.95 



0.03 

 2.52 



.03 

 0.74 







O .07 

 O.14 



9° • 93 

 3-87 

 0.03 

 2 . 52 

 0.66 

 1 . 11 

 0.74 

 0. 14 



A1 2 3 



FeO. .-.'., 



MgO 



CaO 



Na 2 



K 2 



Zr0 2 











Total 



79 J 3 



9-3 6 



312 



8.t8 



O.21 



TOO . OO 



It is quite possible that 20% or less of the feldspar is orthoclase, 

 which would affect the soda-potash ratio perceptibly and the silica- 

 alumina ratio slightly. The composition of the phlogopite may also 

 vary somewhat from that assumed, and is likely to in the iron con- 

 tent more especially. While these uncertainties considerably affect 

 the calculation when regarded as an exact rock analysis, they would 

 affect it in such slight manner, from the standpoint of the general 

 rock character, that it may be regarded as quite certain that we 

 are dealing with a metamorphosed sandstone, slightly aluminous 

 and slightly calcareous, but otherwise entirely normal. 



Associated with the quartz gneisses about Lake Catlin is a much 

 less quartzose rock which is quite micaceous. The thin section 



1 Dana. Syst. Min. Ed. 6, p. 633, no. 8. 



