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NEW YORK STATE MUSEUM 



the oxides of carbon certainly exist in magmas as they are important 

 constituents of volcanic emanations. The experiments of 

 Boudouard 1 with the system CO — CO. in equilibrium, show that 

 on cooling from 1000 to 500 C. at normal pressures CO breaks 

 up in CO L , and " lamp black." 



2 co-co 2 + c 



This form of carbon may be converted into graphite by the appli- 

 cation of pressures and heat, as is illustrated by its presence in 

 gray cast iron. 



Bastin 2 sought to arrive at the temperature at which graphite of 

 the contact type was formed. He examined a suite of specimens 

 from Lead hill, and found that the "quartz was penetrated in a 

 most irregular manner by flakes of graphite oriented in all directions 

 and inclosed numerous crystals of augite. There can be no doubt 

 that the three minerals crystallized contemporaneously." The 

 quartz was examined in the light of the modifications that quartz 

 experiences when subject to thermal changes ; 3 and was found to be 

 in the alpha condition. This indicates beyond reasonable doubt that 

 the quartz, graphite and augite ^crystallized below the inversion 

 temperature of quartz, which is 575 ° C. This temperature is in 

 accord with the experiments of Boudouard and the conclusions 

 reached by Winchell. 



Weinschenk 4 believes that any kind of igneous rock can, if the 

 physical conditions obtain, produce graphite upon contact with any 

 kind of calcareous sediment. The examination of all the contact 

 deposits of the Adirondack strongly supports this view. The 

 Fryatt workings on Lead hill, however, where the sediment is a 

 good clean quartzite seem to question the necessity of limiting such 

 action to calcareous rocks. 



The vein type of graphite. The true fissure veins of Split rock, 

 Lead hill and the Rowland property, as well as elsewhere, indicate 

 that the graphite- forming period continued after the solidification 

 of the pegmatitic-granite, syenite, gabbro or whatever particular 

 series of igneous rock that carried the oxides of carbon. But the 

 graphite is no less magmatic when it occurs in veins than the quartz 

 with which it is associated. The quartz is a hydrothermal product. 



1 Ann. Chim. Phys., 1910, 29:5 



2 Bastin, E. S., Econ. Geol., 5:i34- 



3 Wright, F. E. & Larson, "Quartz as a Geologic Thermometer," Amer. 

 Jour. Sci., 1909, 28:423-77. 



See Fenner, C. N., Amer. Jour. Sci. iv, 36:331-81. 



4 Weinschenk, E.," Mem oire sur l'historie du Graphite" Corrupt. Rend. VIII 

 Congr. Geol. Internat. 1900, p. 447. Zur Kenntniss der Graphitlagerstatten. 



