THE MINING AND QUARRY INDUSTRY I907 3 1 



found in the graphite rock. Owing to their scaly habit and dis- 

 seminated distribution they are somewhat difficult to distinguish 

 from the graphite flakes in hand specimen, though under the 

 microscope they are readily revealed by their transparency. A 

 considerable percentage of mica will be discovered oftentimes 

 in this way when microscopic examination fails to reveal its 

 presence. 



The size of the graphite flakes is another feature that must 

 be taken into consideration. A rock carrying a coarse crystal, 

 other things being equal, is the more desirable, since the econ- 

 omy and perfection of the separation process increase in direct 

 relation to the size of the graphite. The coarse sizes also ooni- 

 mand higher prices in the market than the fine flake, under equal 

 conditions of purity. 



There is considerable variation in the crystallization of the 

 graphite depending upon the character of the gangue. The 

 schists and quartzites of the Adirondacks represent ancient sedi- 

 ments of the nature of sandstones and sandy shales which have 

 been transformed under the influences of heat and pressure 

 while they were deeply buried in the earth. The graphite is 

 traceable to the carbonaceous constituents of plants or animals 

 included in the sediments at the time of their deposition, and 

 its formation which involves a distillation of the organic com- 

 pounds with loss of the volatile parts was an accompaniment 

 of the general metamorphism. It is to be expected that the 

 graphite would show a more perfect crystal development in 

 rocks that have been profoundly changed, and this is, in fact, 

 the case. The schists of the eastern and interior parts of the 

 Adirondacks carry a much coarser flake than the rocks on the 

 western side which have been less metamorphosed. In the 

 deposits of St Lawrence county, on the west, the flake is very 

 fine, at times showing an approach to amorphous graphite. This 

 is, of course, only true with respect to the deposits of organic 

 nature in the sedimentary rocks. The graphite found in veins 

 and dikes is quite uniform throughout the whole region, l)ut 

 such occurrences have little importance from an industrial 

 standpoint. 



GYPSUM 



The ])roduction of gypsum is made in the central and western 

 parts of the State, in Madison, Onondaga, Cayuga, Monroe, 

 Genesee and Erie counties. The gypsum is associated with the 

 Salina formation which carries the rock salt beds and is quarried 



