262 FANNING. 
A variety seen at Sual on Portuguese Point showed an in- 
equigranular porphyritic texture. The rock is very hard, dense, 
and not quite as dark as the variety just described. In thin 
section the rock shows a dosemic porphyroid fabric with pheno- 
erysts of altered feldspar and pyroxene. Magnetite grains are 
abundant. The groundmass is entirely kaolinized. 
In the syenite from Masbate, Iddings? found as accessory 
minerals, mica, apatite; chlorite, epidote, and secondary quartz. 
Apparently the mineralization is more diverse than in the case 
of Pangasinan. It is to be noted that magnetite is more abun- 
dant in the case of Pangasinan, and hornblende is present. 
Diorite.—Diorite is probably an important rock of the region, 
although the specimens collected showed in most cases sufficient 
pyroxene to be classed as gabbros. 
Gabbros.—Gabbros are found in abundance in the area of 
holocrystalline rocks from Sual northward, and also south of 
Barlo. The amount of hypersthene present would class many 
of these rocks as hypersthene gabbros or norites. The rocks are 
of granitic texture, of varying fineness, hard, dense, and mot- 
tled gray to black. In thin section the rocks generally exhibit 
consertal, inequigranular fabric, seriate to intersertal, and con- 
sist of hypersthene, pyroxene, plagioclase feldspar, and various 
minor minerals, hornblende, magnetite, etc. One specimen 
from south of Barlo consisted almost entirely of hypersthene and 
pyroxene and could perhaps be classed as a pyroxenite. This 
specimen showed extensive saussuritization of the few feldspars - 
present. Some pyrite was noted. 
Another specimen from south of Barlo showed pegmatitic 
structure and contained large crystals of plagioclase and light 
green hornblende besides abundant hypersthene. Decomposition 
and microscopical, replacement crystals were noted in this pla- 
gioclase. The pegmatitic structure of this rock was regarded 
with keen interest as it is the first specimen of this type (so 
abundant elsewhere) obtained in the Philippines. 
Peridotite.—A peridotite was found on Portuguese Point, near 
Sual, and in hand specimen this rock is of granitic texture, hard, 
dense, and coal black. Under the microscope the rock ap- 
peared to consist nearly entirely of olivine which shows consider- 
able alteration to serpentine. Some pyroxene and magnetite are 
present, 
Andesites.—Dark porphyritic rocks, probably andesites, are 
"This Journal, Sec. A (1910), 5, 165. 
