GRAPHITE 



281 



difficult if fine grinding is necessary because the 

 mica becomes coated with a film of graphite and is 

 collected along with the graphite, and the grade of 

 the graphite concentrate is thereby lowered. Market- 

 able concentrates generally contain 85 percent or 

 more graphite. 



Probably the largest deposits of flake graphite in 

 the United States occur in gneiss and schist in the 

 Kigluaik Range on the Seward Peninsula, Alaska. 

 The graphitic rocks are exposed for 60 miles along 

 strike, and many layers containing about 10 percent 

 graphite are more than 25 feet thick. Within these 

 layers are lenses and pods containing 50-60 percent 

 graphite, part of which is coarse flake. Most of these 

 lenses and pods are V2-^V2 feet thick and 10-20 

 feet long, but some are as much as 6 feet thick and 

 100 feet long. Within parts of the range, in the zone 

 of graphitic schist, these high-grade pods are esti- 

 mated to make up 25 percent of the rock (Coats, 

 1944). 



Deposits of flake graphite in the United States 

 have been mined in Alabama, Alaska, New York, 

 Pennsylvania, and Texas. 



The world's most economically important flake 

 deposits now in production are in Malagasy Repub- 

 lic, where layers 10-100 feet thick contain 10-20 

 percent graphite. Much of the ore is intensely weath- 

 ered and requires only a simple wash to produce a 

 concentrate containing 85-92 percent graphite. Other 

 important foreign deposits of flake graphite are in 

 Austria, Norway, Russia, and China. 



AMORPHOUS GRAPHITE 



Amorphous graphite, formed by thermal meta- 

 morphism of coal beds, is massive and cryptocrystal- 

 line. The size, grade, and mineral impurities in the 

 deposit depend on the characteristics of the original 

 coal seam. Major deposits being mined today gen- 

 erally contain at least 85 percent graphitic carbon. 

 The material is dried, shipped, and used without 

 beneficiation. Operations are successful only if large 

 quantities of material of reliable quality can be 

 supplied at low cost. The most important single 

 factor in marketing amorphous graphite today is 

 transportation cost. 



In the United States, small amorphous graphite 

 deposits are known in Rhode Island, near Raton, 

 N. Mex., and near Chaffee, Colo. Major free-world 

 sources are Sonora, Mexico, and Korea. 



RESOURCES 



The graphite resources of the world are undoubt- 

 edly great, but their extent is unknown. Reserves 

 are known for a number of operating mines, but rea- 



sonable estimates of potential resources probably 

 are not available for a single major graphite district 

 in the world. The principal reason is that graphite 

 is a relatively abundant and widespread mineral, 

 and known deposits in many areas far exceed cur- 

 rent or foreseeable demands, making it understand- 

 ably difficult to generate interest in making careful 

 resource estimates. As of 1972, deposits containing 

 a total of many hundreds of millions of tons are 

 known, and total world resources may be many times 

 that amount. 



IDENTIFIED AND HYPOTHETICAL RESOURCES 



The identified resources of graphite in the United 

 States as of 1960 are summarized in table 54. So 



Table 54. — Identified resources of graphite of the 

 United States ' 



[Summarized from Cameron and Weis (1960, p. 252) ] 



^ Identified resources are specific, identified mineral deposits that may 

 or may not be evaluated as to extent and grade, and whose contained 

 minerals may or may not be profitably recoverable with existing tech- 

 nology and economic conditions. 



little prospecting and mining has been done since 

 1960 that these estimates of recoverable graphite 

 have not yet been improved. 



Most of the graphitic rocks of Alabama, New 

 York, and Pennsylvania contain less than 5 percent 

 graphite, although a few contain as much as 10 

 percent. The location and ease of mining these 

 deposits suggest that a modest increase in the price 

 of raw graphite might herald the start or resump- 

 tion of commercial production in these States, espe- 

 cially Alabama. The largest domestic graphite de- 

 posits occur in the gneiss and schist in the Kigluaik 

 Range of the Seward Peninsula, Alaska (Coats, 

 1944). These deposits are higher grade than those 

 in the eastern United States, but the greater dis- 

 tance from markets and the greater difficulty of 

 mining them will retard their commercial develop- 

 ment. 



The world's identified and hypothetical resources 

 of graphite are summarized in table 55. 



The best known provinces of vein graphite depos- 

 its are in Montana and Ceylon where the veins cut 

 Precambrian gneiss and igneous rocks. Further 

 search in these areas may reveal additional deposits. 

 The graphitic metamorphic rocks of the Kigluaik 

 Range, Alaska, have been intruded by igneous rocks, 



