GEOLOGY OF THE PARADOX LAKE QUADRANGLE 503 



Of the relative ages of the intrusives, the only evidence is that of 

 somewhat doubtful dikes. Some of the dikes are undoubtedly 

 gabbro and cut all the other Precambric intrusives ; others may be 

 syenites and cut anorthosite, and possibly granite. Granted that 

 these dikes cutting granite are not syenite, the field relations point 

 strongly to the younger age of the granite. Both in this region and 

 elsewhere 1 the syenite is bordered by granite, the granite being much 

 more gneissic than the syenite. Gradations between the two are 

 common. It seems most reasonable to regard the granite as a 

 border development of the syenite, derived from the same magma, 

 and very slightly younger in age. 



Regarded from this point of view the Adirondacks form a well 

 marked petrographic province, presenting rocks with very great 

 variations in composition, grading from ultrabasic to acid, but all 

 to be regarded as derived from one magma by differentiation. 



The great complexity of Adirondack structure results from the 

 fact that these intrusives, together with the sediments of the Gren- 

 ville series, into which they were intruded, have all been crushed 

 so as to present similar planes of foliation, and at a later time have 

 been extensively faulted. 



PART 5 



Economic geology 



Graphite. Graphite and iron ores are the only products of 

 economic importance. The graphite is mined at two localities, and 

 occurs in many places on the quadrangle. The demand for graphite 

 in fine scales is limited, hence the industry has not developed to the 

 full extent of the workable material The mines at the town of 

 Graphite have already been described by Professor Kemp •} the 

 graphite there occurs as drawn-out flakes among quartz grains in a 

 layer bounded above and below by the garnet-sillimanite gneiss. 

 There has been faulting, and the graphite has suffered from a shear 

 along the bedding. At Rock pond, where a small mine has recently 



*H. P. Cushing. "Recent Geologic Work in Franklin and St. Lawrence 

 Counties." N. Y. State Geol. 20th An. Rept 1902. p. r23-r&2. 

 5 N. Y. State Geol. 17th An. Rept 1899. p-539- 



