PLATE XXVIII. 



FIG. 1. 

 ACTINOLITE-SCHIST. 



ELRIGG, STKATH AKDLE, PERTHSHIRE. 



Magnified 50 diameters. Ordinary light. 



The minerals represented are actinolite (8), zoisite ? (21), felspar (10) and 

 rutile (22). 



The needles of actinolite lie, as it were, in a ground-mass composed of a 

 granulitic aggregate of untwinned water-clear grains of a biaxial mineral 

 (felspar). Small prisms and grains of a mineral with high refractive and low 

 double -refractive power (zoisite) are thickly scattered through the slide and occur 

 in the felspar-mosaic and also in the actinolite. The rutile occurs as crystals and 

 grains. A knee-shaped twin (angle made by the principal axes of the two 

 individuals 66) is seen at 22. The felspar-zoisite aggregate answers to the 

 saussurite of Cathrein. 



FIG. 2. 

 EPIDOTE-AMPHIBOLITE . 



NEAR BLACK CROFT, GLEN LYON, PERTHSHIRE. 



Magnified 50 diameters. Drawn with polarizer only; short axis N. and S. 



The minerals represented are hornblende (8), epidote (23), quartz (2-1) and 

 rutile (22). 



The hornblende belongs to two varieties so far as colour is concerned. In 

 the one variety; a= pale yellowish brown, {3= deep green, y= blue or bluish 

 green; in the other a pale yellowish brown, (3 and ^ deep brown. These 

 two varieties are intergrowu. Epidote occurs as idiomorphic crystals and is 

 present as inclusions in both hornblende and quartz. The quartz is present in 

 granular aggregates. It forms a very small portion of the rock. Rutile occurs 

 for the most part in grains. 



