202 
felspar-crystals. The structure may therefore perhaps best be 
characterized as sub-ophitic. 
The order of succession of the dark-coloured minerals is 
very pronounced: iron-ore and olivine are in separate grains 
but both are embraced by augite, and very often a single 
augite-anhedron contains several grains of the two minerals 
first mentioned. Biotite mixed with’ more or less barkevikite 
surrounds the augite and is found as a ‘corona’ round the iron- 
grains outside the augite. This tendency in the dark-coloured 
minerals to embrace one another in regular succession is com- 
mon to the normal varieties of the essexite and the augite- 
syenile (p. 189), and in both rocks the fine-grained border 
varieties show a more even-grained development of the min- 
erals. 
Mechanical phenomena are as a rule absent in the es- 
sexite, in those varieties, however, that show a marked flow- 
structure the labradorite erystals are at times somewhat bent 
or broken. But the mechanical phenomena do not affect the 
augite and orthoclase and must therefore have been produced 
while the rock was as yet semi-fluid. 
Chemical composition. — It will be seen from the preced- 
ing sections that the mineral composition and structure of the 
rock described is tolerably typical of essexite and the same 
holds good from a chemical point of view as it will appear 
from the subjoined analysis (No.18). The specimens analyzed 
have been collected at Panernak Bay, northwest of Narsak 
where the rock had a very fresh appearance. For purposes of 
comparison | give a number of analyses of essexite from various 
parts of the world where the essexite occurs in a somewhat 
similar association of igneous rocks as in South Greenland. 
The agreement especially with the essexite of Essex is very 
conspicuous. As the igneous rocks of the Ilimausak area are 
on the whole distinguished by a high content of iron in pro- 
portion to the regions mentioned in the table on the next page 
