PLATE XLM 



FIG. 1. 

 SCHISTOSE GRANITE. 



PORTHALLA. 



Magnified 35 diameters. Nicols crossed. 



The minerals represented are felspar (10), white or very pale green mica (82) 

 and quartz. 



The felspar occurs partly in the form of large irregular grains and partly as 

 a constituent of a micro-crystalline mosaic. When viewed with ordinary light 

 the large grains appear turbid whereas the small grains are water clear. The 

 light-coloured mica also occurs in two forms, as crystalline plates or scales and 

 as a crypto- or micro-crystalline aggregate. The rock is fissile in the mass. In 

 the microscopic slide the planes of schistosity are defined by the distribution of 

 the white mica. They run from left to right in the figure. 



For a further description of this rock, see page 319 of the text. 



FIG 2. 

 SCHISTOSE GRANITE. 



MARGIN OF WICKLOW MASS, NEAR BALLY BRACK STATION. 



Magnified 25 diameters. Nicols crossed. 



The minerals represented are felspar (10), white mica (32) and quartz. The 

 relations of the constituents are similar to those described above. The portions 

 of the rock in which the parallel structure is most marked are richest in the 

 quartz -felspar mosaic and in the white mica. One of these portions occupies the 

 middle-third of the figure and runs from left to right. This rock contains garnet 

 as an accessory constituent. 



The granite of Wicklow is intrusive in Lower Palaeozoic strata. It is, 

 however, of pre-Carboniferous age. 



