WHITE : OATLAND COMPLEX OF IGNEOUS ROCKS. 115 
Carlsbad twinning is common, and quartz has sometimes 
been forced along the twinning plane (Fig. 2). Some of the larger 
crystals were measured, the dimensions being 2.75 x2.35 mm., 
2.31 X 1.6 mm., 3.78 x 1.45 mm., and 2.5 x 1.25 mm. In the grano- 
diorite the average size would be about 1.4 x. 65 mm. There 
are inclusions of apatite, usually surrounded by iron-ores, grains 
of magnetite, and a few patches of chlorite. The orthoclase 
becomes increasingly turbid by decomposition, the products of 
which, in addition to amorphous matter, are flakes of muscovite 
which lie nearly normal to each other in some sections (Figs. 1 
and 2), and parallel to the sides of the crystal in others. The 
included iron -ores are sometimes altering to sphene. Clear 
bipyramidal quartz is an occasional decomposition product. 
The turbid orthoclase often has a narrow rim of clear felspar 
substance. When orthoclase and plagioclase are in contact it 
is evident that the former has always crystaUised prior to the 
latter. 
The gravimetric proportion of orthoclase in this facies 
decreases from 28 per cent, to 6.1 per cent, of the whole rock. 
Plagioclase usually shows more regular outlines than ortho- 
clase, and has the habit of projecting into the quartz. The 
pinacoids show especially good faces, but some faces are apparently 
corroded by quartz. There are some larger crystals measuring 
about 2.0x1.15 mm., but the average sizes vary from about 
.72 X .4 mm. to 1.1 x9 mm. Twinning according to the albite 
law is common, but there is a gradual assumption of pericline 
twinning as well. The width of the lamellae in the former tjrpe 
becomes slightly increased. The maximum extinction angles, 
measured from the twinning-planes show a gradual increase 
from about 11° to about 16°. The felspar is probably an oligo- 
clase-andesine, but in all the specimens there are some crystals of 
apparently a medium oligoclase. The individuals are turbid 
with decomposition products, but usually have borders of fresh 
felspar substance, sometimes at the ends, sometimes — usually 
when quartz is adjacent, at the sides as well, and sometimes at the 
ends and in interior patches. It is considered that the fresh fel- 
spar is more acid when added to the ends than that on the sides, 
and still more than that in interior patches. The new growth of 
