392 sosMAN AND merwin: data on palisade diabase 



The fragments of rock had an external appearance of incipient 

 fusion. 



Seventy-five minutes at 1225° caused the fragment to flow. 

 About a third of the feldspar remained ; the remainder was glass, 

 containing dark brown octahedral and cubic grains which formed 

 out of the glass. These grains had the high refraction of spinel. 

 Heatings of fifteen and sixty minutes at 1250° fused or fluxed 

 still more of the feldspar but did not remove it entirely. Fifteen 

 minutes at 1302° left only traces of feldspar, and produced a 

 clear glass, of refractive index equal to and slightly less than 1.60. 



With its present composition, therefore,- and under atmos- 

 pheric pressure the diabase can not flow at a temperature below 

 1150° (at which temperature the lowest melting portion probably 

 fuses), and does not flow appreciably below 1225°. It is com- 

 pletely liquid at about 1300°. 



The inclusions. These consist both of feldspathic sandstone 

 and shale. "The thinner portions of the sandstone inclusions 

 are very hard and compact, and look in all respects like fine- 

 grained, light colored granite. . . . From this facies every 

 gradation is found to apparently normal feldspathic sandstone 

 (arkose) in the thicker portions, showing little sign of alteration." 



Fusion of included arkose. We obtained from Professor Lewis 

 a specimen of arkose which had been entirely surrounded by 

 coarse grained diabase under conditions where it must have 

 taken up the temperature of the molten rock, and so situated 

 that it could not have been traversed by mineralizing solutions 

 after the solidification of the rock. This specimen was from the 

 Palisade sill, in the Pennsylvania Railroad cut east of Marion 

 station, Jersey City, where ''thin sheets of arkosic sandstone, 

 perhaps originally continuous, lie in an irregular undulating po- 

 sition in the diabase."^ This inclusion varies in thickness from 

 4 inches to 3 feet (10-90 cm.). The fragments examined were 

 not over 2 cm. from the diabase. 



The metamorphosed arkose consists chiefly of quartz and ortho- 

 clase. New growth of orthoclase is visible around some of the 

 original grains. It is all somewhat dusty, probably from sub- 

 sequent alteration, altho biotite and hornblende, also present, 



^ J. V. Lewis, loc. cit., 1907, p. 135, (4),- and pi. 28. 



