BLACK SANDS OF PARACALE. 215 
s 
second layer of gravel and sand. This was followed by another 
subsidence during which period another layer of clay and loam 
was deposited, and another coral growth was begun near the 
mouth of the river. At the present time an uplift is slowly 
taking place, as shown by the exposure of this coral. It would 
appear that the Paracale has been a tidal river since the deposit 
of the first gravels, with the exception of a possible period when 
the second sand and gravel bed was formed. 
Numerous veins of quartz ore are found everywhere in the 
district, both in the gneiss and schist, but predominantly in the 
gneiss. These veins strike generally about north 10° east, and 
vary in width from a few centimeters to several meters. They 
have been worked by natives quite extensively as shown by the 
large number of pits, shafts, and open cuts in the surrounding 
hills. The natives worked only the surface oxidized ore, owing to 
its soft and free-milling character. The typical unaltered ore of 
the district is clear, white quartz, carrying a large percentage of 
pyrites and generally subordinate amounts of galena. The gold 
and the pyrites found in the alluvium were principally derived 
from the erosion of these veins. The magnetite and ilmenite 
came partly from the veins, but mostly from the country rock. 
The alluvium is made up of layers of clay, clayey sand, and 
gravel. An occasional layer of tough blue clay near the gravel 
causes trouble in dredging by carrying away metallic gold 
which it picks up as it passes over the tables. Many of the 
quartz fragments in the gravels contain visible gold. Some have 
been found with pockets of crystallized gold out of which from 
20 to 30 grams of gold were taken. Contrary to what would 
be expected, the coarser fragments are found near the mouth of 
the Paracale River. Many well-rounded, water-worn boulders 
were found which weighed almost a ton. These decrease in 
size toward the west, and are very small in the upper portion of 
the deposit. This is probably due to the fact that the boulders 
have come from the quartz veins of the side hills. Two sections 
of this alluvium have been described in the Mineral Resources of 
the Philippine Islands. The first, described as near Paracale,* 
has in vertical section: 
From 4 to 5 meters of barren clay and loam. 
A few centimeters of coral in places. 
Gray clay, irregular in thickness, carrying values. 
Sand, gravel, and quartz fragments; irregular in thickness, rich in gold. 
The bed rock is soft decomposed schist. 
*Ferguson, H. G., Min. Resources P. I. for 1908, Bur. Sct., Div. Min. 
(1909), 22. 
