﻿Vol. 64.] EOCKS OF GLEirDALOUGH AND GREYSTONES. 



48a 



actinolite, and grains of sphene occur within the larger flakes 

 (fig. 4). 



A pale-brown mica occurs sparingly, in small flakes inserted 

 between the actinolite-fibres or within the larger ones. The 

 minerals of the epidote-group consist, for the most part, of granular 

 clinozoisite collected in irregular patches which are penetrated by 

 needles of actinolite. But there is also a coloured mineral of 



Fig. 4. — Actinolite-rocJc from Glendalough, showing actinolite, 

 sjphene, pyrnte, and zoisite. (Magnified 30 diameters.) 



m 



[Z= Zoisite ; S = Sphene.] 



rectangular form, exhibiting pleochroism from deep to pale brown, 

 with lateral outgrowths of clinozoisite, properties characteristic of 

 allanite. It has produced a pleochroic halo in the surrounding 

 actinolite.* Small halos round indeterminable grains are believed 

 to have the same origin. 



(4) The Zoisite-Amphibolite. 



These rocks contain poecilitic crystals of hornblende, enclosed in 

 a granular matrix which is white with zoisite. Sulphides are 

 abundant. The specific gravity is 3*00. 



Within the amphibolite runs a vein, about an inch wide, of a 

 water-clear clinozoisite and a dull felspar. The cHnozoisite forms 

 stout prisms with square section, and well-defined crystal-faces 

 moulded by the felspar (J inch diam. x J inch). Often the vein is 



