198 
irregular lamellæ arranged in the same manner as in an ordi- 
nary orthoclase-microperthite. The quartz is allotriomorphic 
and is present in about the same proportion as the felspar. The 
anhedra are of considerably smaller dimensions in this granite 
than in the adjoining quartzitic sandstone. The arfvedsonite is, 
apparently by magmatic resorption, very extensively altered to 
ægirine with numerous inclusions of black ferruginous material. 
ESSEXITE. 
The essexite covers a small area of almost two square 
kilometers along the coast by the Narsak settlement. On the 
opposite coast it appears again at Sigsardlugtok, about seven 
kilometers west of Narsak and in Sermilik Fjord it is found at 
Kangerdluak. It is a coarse-grained dark gray rock whose 
main component, a plagioclase, is developed in large tabular 
crystals. The occurrence of the rock and the variations in 
its appearance have been described at length in a former chapter 
(psig): 
Microscopic characters. — Under the microscope the mi- 
nerals seen are: apatite, iron-ore, olivine, augile, hornblende, 
biotite, labradorite, orthoclase and secondary products. Nephe- 
line has not been observed. 
The apatite is relatively abundant in prisms of the usual 
form. The crystals may reach a length of 5 millimeters and a 
thickness of 0°5 millimeter. The iron-ore occurs in consider- 
able amount; it is in crystals and irregular grains sometimes 
measuring several millimeters across. It is titaniferous and 
gives rise to secondary titanite. In the pseudomorphs a frame- 
work of unaltered iron-ore indicates that the original ore had 
a lamellar structure’. It is usually bordered by a fringe of 
scaly biotite. 
! The pseudomorphs agree with those figured by RosexBuscH (Mikrosk. 
Physiogr. I, 2, Pl. II, 6 (1905)). 
