[ 48 ] 



VI. 



ON A FKAGMENT OF GAENET HOENFELS. 

 SOLLAS, LL.D., F.E.S. 



By PEOFESSOE 



[Read December 17, 1890.] 



The rock under description occurs as a thin band, not more than 

 half an inch in thickness in the Ordovioian schists adjacent to the 

 granite of Oarrickmines. The exact spot where it is exposed I do 

 not know and cannot now discover, since Mr. Dobbin, B.E., to 

 whom I am indebted for the fragment which came under my 

 notice, is absent in America. The specimen was of no great size, 

 less than an inch square measured over the bedding plane : a thin 

 slice cut at right angles to the bedding was prepared for micro- 

 scopical examination, the remainder furnished just enough material 

 for analysis. I regret not to have had more at my disposal, as I 

 should have liked to repeat some of the analyses. 



The general appearance of the rock is that of a garnet-hornf els, 

 light- grey in colour, speckled with minute cinnamon- coloured 

 spots, due to included garnets. Its specific gravity as determined 

 by Mr. Doyle, B.E., to whom I am indebted for assistance in 

 making some of the analyses, is 2 '925. It yielded to analysis 

 the results given in column I. 



101-194 99-88 99-13 



