THE MINING AND QUARRY INDUSTRY 



77 



In St Lawrence county graphite is associated with crystalline 

 schists in deposits similar to those on the eastern side of the Adiron- 

 dacks. The Macomb Graphite Co. has developed a property near 

 Pope Mills, town of Macomb. A mill was erected in 1904, but it 

 was not operated last year, except experimentally. The graphite 

 occurs as fine scales in schist and the deposit is said to be extensive. 



Separation of graphite. The separation of graphite when it 

 occurs in disseminated flakes is a matter of considerable difficulty. 

 Crystalline graphite has a specific gravity of about 2.25, which is 

 less than that of the accompanying minerals, though the difference 

 is not so great that concentration by gravity methods can easily be 

 effected. The separation is frequently complicated in the case 

 of the Adirondack deposits by the presence of other scaly minerals, 

 chiefly mica and chlorite. While various processes have been de- 

 vised and employed at different times by companies operating in 

 this region, those now used are based on the principles of wet 

 concentration, that is, crushing and separation by water. For 

 crushing, both California stamps and rolls are employed. The 

 former seem to be better adapted to the hard quartzite than to the 

 softer schist or limestone. After crushing sufficiently fine to release 

 the graphite from its matrix, the material is washed in stationary 

 buddies. In some mills a shaking table such as is used in the con- 

 centration of metallic ores precedes the buddle. The table takes 

 out the coarse particles of the heavy minerals as concentrates, while 

 the slimes and graphite are carried away in the overflow. The 

 middlings from the first buddle are retreated, and the separation is 

 continued until a product assaying 70 to 75 per cent graphite is 

 obtained. The graphite is dried, bolted and subjected to a refining 

 process for removal of the remaining impurities. Pneumatic 

 methods and flotation on water are said to be used in refining, 

 though few details as to actual practice have been made known. 

 In its final preparation for market the graphite is polished and 

 graded into sizes. 



Production. The production of crystalline graphite in 1905 

 amounted to 3,897,616 pounds, valued at $142,948. The output was 

 contributed by three companies, viz American Graphite Co., Colum- 

 bia Graphite Co. and Adirondack Mining & Milling Co. In the 

 previous year the output aggregated 3,132,927 pounds valued at 

 $119,509. The average price for 1905 was 3.7 cents a pound, 

 against 3.8 cents a pound for 1904. Since the beginning of the 

 present year the Champlain Graphite Co. and the Macomb Graphite 

 Co. have started operations at their mines and mills. 



