82 NEW YORK STATE MUSEUM 



into a basic (quartzless) syenite which contains garnet crystals up 

 to an inch or more across but never with hornblende rims, and 

 this rock in turn grades into the typical country rock of syenite 

 which is somewhat garnetiferous. The writer is fully convinced 

 that this transition zone (wall rock) has been formed by the as- 

 similation or actual melting or fusing together of the syenite and the 

 border of the great inclusion at the time of the intrusion of the 

 syenite. In hand specimens and in thin sections, as shown in the 

 field, the garnet rock at the Hooper mine is almost exactly like this 

 wall or transition rock of the Rogers mine and it also appears to 

 grade into the country rock. In the Hooper mine this transition 

 rock makes up practically the whole mass of rock which is mined 

 and is hence much more extensive than at the Rogers mine. All 

 evidence strongly points to the origin of the Hooper mine rock as 

 due to rather thorough melting together of an admixture of syenite 

 and Grenville hornblende gneiss where the Grenville inclusion was 

 perhaps deeper down in the magma and hence subjected to much 

 greater heat, or possibly a number of smaller hornblende gneiss 

 inclusions were assimilated by the molten syenite or granite. 



GRAPHITE 



Within the map limits but one graphite mine has ever been in 

 actual operation, though prospect holes have been made at various 

 places. The mine, including an open pit and short tunnel and 

 separating mill, is located i mile southwest of Johnsburg. The 

 graphite occurs in small flakes in gray, thin to thick bedded, Gren- 

 ville gneisses which are usually very rich in quartz. A detailed 

 description of specimens from this mine has been given on page 14. 

 Some graphitic limestone was taken out from near the mine en- 

 trance. The rocks strike north 70° east and dip 35° to the south. 

 This mine was worked as late as June 1910 but apparently has not 

 been very successful. An interesting feature is a quartz vein up 

 to a foot wide, which cuts across the graphitic beds at a high angle 

 and which contains rich seams (as much as an inch wide) of pure 

 graphite. The mine superintendent stated that in 1899 one piece 

 of graphite weighing 543 pounds was taken out. Excellent speci- 

 mens of associated quartz and graphite may be obtained from the 

 mine dumps. 



A prospect hole 2}4 miles due south of Pottersville and close 

 to the road was opened in limestone some years ago. Some of 

 the limestone beds are pyroxenic to serpentinous. The limestone 

 contains occasional flakes of graphite up to one-half of an inch 



