THE ADIRONDACK GRAPHITE D.EPOSITS 14^ 



containing lignum, that is, vascular plants, apparently do not appear 

 until the Lower Devonian and hence algae 1 are called upon to supply 

 the carbon. ( hi the decay of such plants an odoriferous thick oil 

 ("sapropelic" matter) results that can be regarded as akin to 

 bitumin ; hence the writer prefers the term " bituminous sand- 

 stone." The habitat of these algae seems to have been shallow water 

 near the shore. This view is strengthened by the gradual dis- 

 appearance of the Faxon limestone to the east and its replacement 

 by metaarkoses and metagraywackes, indicating that the shore of 

 the Grenville sea at Dixon-Faxon time was to the east. 



All the specimens of the graphite schists (all types) studied 

 revealed considerable amounts of pyrite. A large proportion of 

 this has been introduced; two distinct periods are clearly recogniz- 

 able, especially in case of the Rock Pond ores where an excessive 

 amount permits easy observation. A small amount, however, 

 appears to have been an original constituent in the argillaceous 

 sandstones, or that the iron content was in the form of chloritic 

 minerals. During metamorphism " much of the iron is reduced to 

 the ferrous condition . . . and it may . . . combine with 

 sulphur, which is often present under these conditions, to form 

 pyrite. The presence of ' carbonaceous matter ' favors this reduc- 

 tion, as shown by the common association of sulphides 

 with graphitic shales." 2 Smyth 3 points out the close genetic rela- 

 tions of pyrite and graphite. That graphite, as such, or as organic 

 carbon, having the property of precipitating the pyrite has been 

 pointed out by Von Cotta 4 and Jenny. 5 Smyth says: " Thus, for 

 the graphite, a history somewhat similar to that of the pyrite is 

 indicated, but with the difference that most of the former is thought 

 to be carbon that was original in the sediments, which has under- 

 gone some concentration and may have received minor additions 

 from magmatic sources, [see later] while, in the case of the pyrite, 

 the relative importance of these sources is reversed." Thus the 

 evidence furnished by the pyrite would add support to the con- 

 tention that the carbon was present in the sediments as an original 

 constituent. 



1 White, David, Econ. Geol., 3:298; Osborn, H. F., "The Origin and the 

 Evolution of Life," 1917, p. 50, fig. 5. 



2 Leith, C. K., & Mead, W. J. " Metamorphic Geology," 1915, p. 104-5. 



3 Smyth, C. H., jr, " Origin of Certain Adirondack Pyrite Deposits," 65th 

 Ann. Rep't, N. Y. State Mus. 191 1, 1 : 174 et sec. 



4 Von Cotta, " Treatise on Ore Deposits," Eng. Trans, p. 46-47. 



5 Jenny, W. P., " The Chemistry of Ore Deposition," Trans. Am. Inst 

 Min. Eng., 1903, 33:455-57- 



6 Ibid, (see p. 182) footnote. 



