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LXIX.— ON THE OCCUEEENCE OF BEEYL WITH SCHOEL 

 IN GLENCULLEN VALLEY. By PEOFESSOE J. P. 

 O'EEILLY. 



[Read, June 15, 1885.] 



In the mineral collections existing in Dublin may he found speci- 

 mens of beryls, from various places in the neighbourhood of 

 Dublin where granite occurs. Samples from Dalkey Quarries, 

 from the Three-Rock Mountain, from places in Wicklow, such as 

 Grlenmalure and Glenmacannus, have been mentioned. The speci- 

 mens now shown were found in quarries, known locally as the 

 Kearneystown Quarries, situated in the GrlencuUen Yalley, near 

 GrlencuUen Bridge, on the south side of the stream. These quarries 

 are opened in granite, and have been worked for some time, so 

 that the excavations are extensive, and show a considerable front 

 of rock. The distance from the stream is about eighty to one 

 hundred yards, and in the principal quarry there exists a joint or 

 fissure which, so far as I could judge, is parallel to the course of 

 the stream, presenting a direction about N. 62° 40' W. (being the 

 same as that of the group of jointings which I described as occur- 

 ing frequently in the environs of Dublin with a mean direction of 

 N. 60° 41' W.). This joint is filled in certain parts of the quarry 

 with what is called " rotten stuff " by the quarrymen, that is, 

 granite much broken and decomposed, and presenting in several 

 places along its direction, bunches of schorl, large crystals of 

 orthoclase and muscovite mica, these assuming a somewhat plumose 

 arrangement. At one particular point a rock was detached, which 

 contained not only these minerals but also well-marked crystals 

 of beryl. The quarrymen threw it aside, and broke off some of 

 the stuff. The large bunch I secured, and it is now in the gallery 

 of the Royal College of Science. The small hand samples now ex- 

 hibited show the crystals with some well-marked forms of the prism 

 and basal section ; at the same time it is clear that the interior 

 of the crystals is not homogeneous, and has undergone a certain 

 amount of decomposition. It is evident that these crystals were 



