THE ADIRONDACK GRAPHITE DEPOSITS $1 



True fissure veins. Besides the contact type of graphite, the 

 mineral occurs " in narrow veins from one to two inches wide, mosl 

 of which are vertical and trend nearly north and south. They cut 

 indiscriminately across the schists and pegmatitic granite, but in a 

 number of cases apparently disappear when crystalline limestone is 

 reached. In them graphite is usually the only mineral recognizable 

 and forms aggregates of nearly parallel blades arranged about at 

 right angles to the walls of the vein and closely resembling certain 

 of the Ceylon occurrences. In most places the walls are sharp, and 

 the pegmatitic granite shows no change of texture next to the vein. 

 In a few places, however, the pegmatite becomes pyroxenic, finer 

 grained, and somewhat graphitic next to the vein." 1 



" Kemp describes the graphite deposits ... as true fissure 

 veins cutting the laminae of the gneissic walls at nearly right angles. 

 The wall rock is a garnetiferous gneiss with an east and west 

 strike, and the vein runs at the big mine 12° west with a dip of 55 ° 

 west. The vein filling is evidently orthoclase (or microcline) w r ith 

 quartz and biotite and pockets of calcite. The mineral is also asso- 

 ciated with tourmaline, apatite and sphene [titanite] ." 2 



The deposit on Lead hill has been popularly referred to as a 

 " vein " or as a " dike." While it is true that very small veins do 

 occur, the important graphite rocks are contact rocks, and not veins. 

 The former do not extend in any definite direction such as is implied 

 by the word " vein " or " dike." .This matter is brought to the 

 attention of the reader with the hope that the past nomenclature, 

 which is clearly erroneous, may be corrected. 



Split Rock Prospect 



This is in Essex county, in the township of Essex, 8 miles north- 

 east of Westport, within the Willsboro quadrangle, 30 to 40 rods 

 south of the Split Rock Light House. 



Workings. These consist of (1) a prospect pit verging upon a 

 vertical shaft about 20 rods from the shore at an elevation of 60 

 feet above Lake Champlain, and (2) an opening for a drift on the 

 lake shore, east of the pit. It is believed that an attempt was made 

 to sink a shaft, which the pit represents, to join the horizontal drift. 



Geology. The northern and eastern shore of the point shows 

 members of the sedimentary or Grenville series of rocks which 

 include schists and garnet gneisses, associated with crumpled 



1 Bastin, E. S., Mineral Resources, U. S. G. S., 1908, 2:730-31. 



2 Cirkel, Fritz, " Graphite," Can. Dep't of Mines, Mines Br. 1907, p. 56. 



