132 



H. S. JEVONS, H. I. JENSEN AND C. A. SUSSMILCH. 



In addition to these two large segregation veins there 

 are a number of smaller veins situated above, between and 

 below them, running in no general direction and seldom 

 more than two or three inches in thickness ; ODe of these 

 is shown in figure 2, branching off from one of the larger 

 veins. These smaller veins in nearly all cases, contain 

 essexo-aplite only. None of the segregation veins extend 

 into the more compact part of the zone of pallio-essexite. 



The two rock types occurring in the segregation veins 

 are notably different from the essexite, and differ also from 

 one another. The mineral composition of these two rocks 

 together with some of their physical characters, are set 

 out for comparison in the following table : — 



Table IT. 



(1) Essexite. 



(2) Essexo-pegmatite. (3) Essexo-aplite. 



Grainsize 0*5 - 3 mm. 



(a) 2*5 — 3 mm. 



(a) 0-1-0-15 mm. 





(b) 5-10 „ 



(b) 0-25-075 „ 



(c) 1-2 „ 



Fabric Hypidiomorphic 



Hypidiomorphic 



Hypidiomorphic to 



granular 



granular 



panidiomorphic 



Average- Mineral 0/ 

 Composition. / Q 



Orthoclase nil 

 Albite nil 



% 

 nil 



33-5 



granular 



% 



j nil in the mode 

 ( 17*10 in norm. 

 60-46 



Labradorite 37*2 



50-0 



nil 



Pyroxenes (augite) 40*5 

 Olivine 4-9 



augite \ 

 diopside L 11 -0 

 segerite ) 



nil 



diopside > 17-47 

 aegerite - 

 nil 



llmenite 16-6 



5- 



4-38 



Apatite 0-7 



0-5 



06 



From this comparison we see that in passing from the 

 normal essexite to the centre of the segregation veins we 

 meet with — 



