,^6 NEW YORK STATE MUSEUJH: 



feet in thickness. The bed and associated strata are traceable 

 from near Lake Champlain west to Johnsburg in Warren county, 

 a distance of 25 miles, and from the towTi of Hague, Essex county, 

 south to Saratoga Springs, a distance of 40 miles. The graphitic 

 rock does not occur as a continuous belt but in more or less isolated 

 patches which represent the broken and eroded remnants of what 

 were once probably continuous beds. The rock has been folded 

 into anticlines and synclines, injected by various igneous rocks and 

 faulted and dissected so that its present distribution is irregular. 



In most of the deposits the graphite rock has the characteristics 

 of a quartz schist. The average composition of the schist is about 

 60 per cent quartz, 20 per cent feldspar, 6 per cent graphite, 3 per 

 cent pyrite and 3 per cent mica, with accessory minerals of smaller 

 amounts. The foot wall of the bed is usually a feldspathic quartzite 

 which in some places may contain more or less garnet, as instanced 

 by the foot wall of the American mine at Graphite. Below this is 

 hornblende schist or amphiboHte. On top of the graphite rock and 

 in some places interbedded vfith it as well is crystalline limestone; 

 the limestone, however, is frequently absent in the graphite localities 

 in the eastern part of the Adirondacks. Lying above the limestone 

 is a thick bed of quartzite. 



Mining. The graphite rock seldom occurs in such position that 

 it can be worked to advantage by open cut methods. The deposits 

 are thin as compared with their length and breadth and usually 

 have a heavy cover. The seams are tilted horizontally at angles 

 ranging from 5° to 10° up to verticality, and rarely follow a uniform 

 dip for long distances underground but roll and pitch after the 

 manner of folded beds. Mining consequently .has to be carried on 

 undergroimd, although at the outset the exposed edges of the 

 schists may be attacked by open cut methods if the rock is not too 

 badly disintegrated by weathering which not infrequently is the 

 condition owing to the presence of pyrite. Underground the beds 

 are followed by inclines sunk on the foot wall, the angle of the incline 

 conforming with the dip. On either side of the incline the rock is 

 mined out in great chambers to the height of the bed. No timber 

 is used and the pillars are usually placed wide apart as the roof is 

 strong. Except for the variable dip of the beds which complicates 

 the mining operations to some extent the conditions are favorable 

 for economic working. 



Separation. Various methods for the extraction of the graphite 

 from the gangue have been practised in 'the Adirondacks but most 

 of the mills have been designed for a wet process in which the main 



