158 
and, as a consequence, stand out in relief from the aplite in 
which they are enclosed. They occur apparently quite 
irregularly arranged in the mass, but appear with few excep- 
tions to be confined to the finer-textured variety of the aplite. 
In section, as seen on the rock face, they appear more 
or less elliptical, although some are really hexagonal. e 
form taken by the majority of the nodules is, however, an 
ellipsoid. In size they are slightly variable, but the greater 
number have diameters, approximately, of 2 in., or slightly 
less. 
A number of thin sections of these nodules was cut, and 
microscopical examination showed them to consist, essenti- 
abundant, and is characteristically developed in the act e 
replacing the microcline and albite felspar. All stages 0 
replacement. Minute arms of tourmaline stretch, at intervals, 
ain. roportion of quartz in such enr 
may increase at the centre, suggestive of silica being der 
from the felspar interaction. : pus 
.  JNodules somewhat similar to those just described eee 
been previously noted by investigators of the Tasman n 
Geological Survey. "Waller(2 noted their occurrence 12 
i More r 
_, Cf. Mem. Geol. Surv. Eng. and Wales, 1909, p. b 
M art Journ. Geol. Meg vol. lix., 1903, p. ne n. 
m. V Waller: Re on the Tin Ore Deposits of Moun 
kirk, Geol, Surv. ras, Sept., 1902, p. 4. 
