BL/EOLITE- SYENITE. 193 



The plagioclase in this rock agrees in presenting these charac- 

 ters, and it resembles very closely that which forms the narrow zones 

 separating the elaeolite from the microperthite in the coarse-grained 

 veins (p. 22). Until its characters can be worked out more fully, 

 therefore, this mineral may be referred to albite. 



The relations of the white minerals in this rock are of a most 



Oscillations in the order irre S ular kind - Rounded lumps of elaeolite are 

 of crystallization. found j n both albite and m ; croc ij ne# Irregular 



shreds of albite are often found scattered through microcline, having 

 an optical parallelism with one another as well as with an adjoining 

 large, well-twinned albite crystal. On the other hand, isolated lumps 

 of microcline, crystallographically parallel to an adjacent large 

 crystal, are found lying in the albite lamellae. And yet there is no 

 definite granophyric structure, nor is there any approach to poikilitic 

 structure. The rock may, however, have possessed the former 

 structure and may have since become granulated by disturbance 

 during, or by crushing after, consolidation. The very imperfect local 

 approaches to granophyric intergrowth lend colour to this view, 

 which is supported by the crystallographic parallelism so frequently 

 observed in the two mutually entangled felspars. The fact that the 

 elaeolite crystals, occurring as merely isolated rounded lumps in 

 both felspars, never show any trace of crystal outline would suggest 

 a corrosion and trespass by the felspar ; in fact the structures in this 

 rock suggest altogether an imitation of the processes which gave 

 rise to the narrow bands of albite seen so frequently to separate the 

 elaeolite from the potash-felspar crystals in the coarse contempo- 

 raneous veins. There has been corrosion of some sort, but the evi- 

 dence is not sufficiently abundant to be conclusive as to the direction 

 in which the changes have taken place. This sort of contradictory 

 evidence as to the order of succession amongst the constituents 

 seems to be quite characteristic of some members of the crystalline 

 schists. The pyroxene-granulites, for example, are especially prone 

 to inconsistencies in the order of crystallization of their minerals. 



( 35 ) 



