The Origin and Relations of the Carbon Minerals. 281 



anthracite.' Similar anthracitic asphalt or asplialtic anthracite 

 is common in the Calciferons sand-rock in Herkimer County, 

 New York, where it is associated with, and often contained in, 

 the beautiful crystals of quartz for which the locality is famous. 

 Here the same phase of distillation is reached as in the coke 

 residuum of the petroleum stills. 



Finally, in some crystalline limestones, detached scales or crys- 

 tals of graphite occur, which are undoubtedly the product of the 

 complete distillation of liquid hydro-carbons with which the 

 rock was once impregnated. The remarkable jourity of such 

 graphite is the natural result of its mode of formation, and such 

 cases resemble the occurrence of graphite in cast iron and basalt. 

 The black clouds and bands wdiich stain many otherwise white 

 marbles are generally due to specks of graphite, the residue of 

 hydro-carbons which once saturated the rock. Some limestones 

 are quite black from the carbonaceous matter they contain 

 (Lycoming Valley, Penn., Glenn's Falls, N. Y. and Collingwood, 

 Canada), and these are sold as black marbles, but if exposed to 

 heat, such limestones are blanched by the expulsion of the con- 

 tained carbon ; usually a residue of anthracite or graphite 

 is left, forming dark spots or streaks, as we find in the clouded 

 and banded marbles. 



In the preceding remarks, no effort has been made even to 

 enumerate all the so-called carbon minerals which have been de- 

 scribed. This was unnecessary in a discussion of the relations 

 of the more important groups, and would have extended this ar- 

 ticle much beyond its prescribed length. Those who care to 

 gain a fuller knowledge of the different members of the various 

 groups, are referred to the admirable chapter on the "Hydro- 

 carbon Compounds" in Dana's Mineralogy. 



It will however add to the value of this paper, if brief mention 

 be made of a few carbon minerals of which the genesis and re- 

 lations are not generally known, and in regard to which special 

 interest is felt, such as the diamond, jet, and the hydro-carbon 

 jellies, "Do2:)plerite," etc. 



The diamond is found in the debris of metamorphic rocks in 

 many countries, and is probably one of the evolved products of 

 the distillation of organic matter they once contained. Under 

 peculiar circumstances it has aj)parently been formed by precip- 



