Vol. 56.] IGNEOUS ROCKS OF COUNTY WATERFORD. 681 



end of Garrarus Strand). Some of the rocks exhibit a few of fel- 

 spar; in others the phenocrysts are larger and more numerous, 

 and mostly of plagioclase, some with very fine albite-twinning and 

 extinction-angles of 12° to 15°, others with less frequent twinning 

 and larger extinction-angles of 18° to 20° (Garrarus Strand). 



Some of the cryptocrystalline felsites without phenocrysts from 

 this locality show flow-structure; others with phenocrysts 

 show this structure; and perlitic structure is found in many 

 (Lady's Cove, Garrarus), the cracks being filled with a pale-greenish 

 material as in the microcrystalline examples. In one case, portions 

 of the cryptocrystalline groundmass are composed of minute micro- 

 spherulites which give a distinct black cross with crossed nicols. 



There is one cryptocrystalline felsite from Lady's Cove, Garrarus, 

 which deserves separate mention because the porphyritic felspar- 

 crystals in it have been converted into a clear coarse granular 

 aggregate which still retains the original outlines of the crystals. 



Another felsite, the nodular rock near Bunmahon (p. 669), has 

 its groundmass almost wholly isotropic, and only a few small quartz- 

 crystals occur as phenocrysts. Here may be mentioned a perlitic 

 felsite from Lady's Cove, Garrarus, with likewise a nearly isotropic 

 groundmass, thickly set with small angular grains of clear quartz, 

 and containing also a few large porphyritic felspars with rounded 

 angles. 



Some of the felsites with a cryptocrystalline groundmass contain 

 xenoliths of other felsites ; especially is this the case with the 

 greenish felsites between Kilfarrasy and Green Island and around 

 Annestown, in which xenoliths are very abundant as well as 

 phenocrysts of felspar (pp. 663-65). 



The micropoikilitic type of groundmass (Type C) is occa- 

 sionally found. Dr. Hatch * mentions several examples. In some 

 cases (Lady's Cove, Garrarus, and Sheep Island) this structure only 

 occurs in disconnected patches in a generally microcrystalline 

 groundmass, and the mosaic is fine and blurred. Numerous 

 crystallites, globulites, and margarites, and a few large porphyritic 

 orthoclases and plagioclases with rounded angles occur in these rocks. 

 In another from Garrarus with similar groundmass there are scarcely 

 any phenocrysts. In another case from Kilfarrasy, in addition to 

 felspar-phenocrysts a few large rounded quartz-crystals are seen, 

 round which a fine radial growth has formed ; the groundmass is 

 almost wholly micropoikilitic, but parts are pseudospherulitic. 

 Indeed the micropoikilitic patches in the rock previously mentioned 

 frequently show radial structure, and the groundmass of some of 

 these patches appears to consist of closely-packed, irregularly- 

 defined pseudospherulites. The blurred micropoikilitic groundmass 

 of a dyke on Knockane Strand shows traces of similar structure. 



Occasionally the groundmass is regularly micropoikilitic without 



any phenocrysts (Kilfarrasy), or with very few, apparently of ortho- 



clase (Morageeha Strand). A beautiful example of the coarser 



type with granophyric structure developed in each patch of the 



1 Geol. Mag. 1889, p. 547. 



