48 NEW YORK STATE MUSEUM 



southward, continuing onto the lot owned by the American Graphite 

 Company. The Algoman gabbro which outcrops so frequently on 

 the southern edge of the area mapped has intruded the sediments 

 as mushroom- shaped bodies (laccoliths), doming up the Swede 

 Pond quartzite. Just where the feeding channel or channels (the 

 " stem of the mushroom ") of the mass of gabbro on the lot is of 

 course not known, but it may be that they cut through the ore at 

 some point underneath the surface. 



The Dixon schist. This is a sedimentary rock composed of 

 interlocking quartz grains with accessory microcline and oligoclase 

 feldspars (usually altered to sericite), pyrite, graphite and bleached 

 brown biotite; in part completely altered to chlorite. Occasionally 

 a little apatite, titanite, zircon and garnet is found. The graphite is 

 almost always associated with the biotite, usually interleaved with 

 it, and frequently with the pyrite as well. The graphite, biotite and 

 pyrite occur in bands parallel to the schistosity. 



Chemical analysis of the American ore 



SAMPLE A SAMPLE B SAMPLE C 



SiO* 65.10 



AI2O3 9-15 



Fe 2 3 4.68 



FeO 3 09 



MgO 2.21 



CaO 1. 17 



Na 2 .24 



K 2 2.32 



H 2 — .50 



H 2 + 2.33 



TiO .96 



C0 2 None 



P 2 0, .74 



S 3-26 



MnO .03 



C 5-29 Graphite. ..6.25 5.36 



Total 101.61 



Less O '. 1 . 63 



99.98 



Sample A is a composite sample analyzed by George Streiger in 

 the laboratory of the United States Geological Survey. Collected 

 by E. S. Bastin. 1 Sample B is another collected by Bastin (Econ. 



1 Bastin gives this analysis in Econ. Geol., 5 : p. 141. F. W. Clarke, U. S. 

 G. S. Bui. 591, p. 40, gives the identical analysis for the Adirondack Graphite 

 Company's (Washington co.) ore. As it seems highly improbable that the schists 

 of the two localities should be exactly alike, it seems very likely that some error 

 has occurred in ascribing the analysis to both companies. It seems probable 

 that this analysis was made upon the American Graphite Company's schist. 



