182 



Proceedings of the Royal Irish Academy. 



combined ; but at the apex there is a great predominance of the 

 pyiite. 



Fig. 5. 



Fie:. 6. 



From the slices examined, the peculiaiities of this elvanyte seem to 

 be the nearly total absence of mica, except in nests, while the crystals 

 or blebs of quartz, so characteristic in general of elvanytes, are nearly 

 microscopic. The incipient crystalline forms in the felspathic matrix 

 are also remarkable. But, as before mentioned, the specimens ob- 

 tained were more or less weathered, and taken fi-om near the margin of 

 the mass. If, however, normal specimens could hare been procured, 

 and from places more deeply seated, it is probable that the poi'phyiitic 

 characters would be better developed. 



