468 
Philippine Jom'nal of Science 
1919 
and average width of the underwater deposit is not known, as 
no soundings were made. The depth of the concentrated sand 
between the high- and the low-water marks is over a meter, and 
there are wells above the shore line in the vicinity of Looc that 
have clean sand bottoms at a depth of from 2 to 3 meters. In- 
sufficient data are at hand to make even an approximate estimate 
of the total amount of sand available. 
The deposits of vein-quartz gravel and bowlders are found 
along the coast bordering the schist and gneiss formation at 
the north and the south sides of the intrusive granite mentioned 
above. The gravel has accumulated in great quantities in all 
the inlets, and the supply is fairly large. The principal areas 
of accumulation are the northern shore of Looc Bay toward 
Tumbaga Point, and from Antipolo Point to Pula Point near the 
town of Agcauayan. It is also found on the east shore of Lubang 
Island from Caybanac Point to Quebrada Point, and around the 
southern shore from Natulo Point to Balacbaiac Point. Patches 
of accumulated quartz gravel are also to be found on the northern 
shores of Golo Island from Bulacan toward Caypandan Bay. This 
gravel ranges in size from that of a pea to more than 75 milli- 
meters in diameter and is mixed with quartz bowlders weighing 
from a few kilograms to a ton or more. The gravel and the 
bowlders come from the fracturing of the segregated lenticular 
veins of quartz found in the schist and the gneiss. Some of the 
quartz lenses outcropping in Dilau Point measure approximately 
6 meters in thickness. However, the main supply of these quartz 
veins is found around Agcauayan, where several lenticular veins 
outcrop, and floats of quartz breccias and bowlders cover the tops 
of Agcauayan, Puti, and Pula Hills (see fig. 1). 
Besides the materials above desjcribed, the discharge slimes 
from the cyanide treatment of auriferous quartz of the Colorado 
Mining Company cyanide mill located at Aroroy, Masbate, and 
other such mills, may prove to be of value as a possible source of 
silica in glass manufacture. The utilization of this pulp has the 
advantage that, being already finely pulverized, it can be mixed 
directly with lime and alkali without preliminary treatment. Al- 
though no actual test has been made of this material, we are of the 
opinion, judging from its chemical composition, that it will make 
a good bottle glass. 
Sand of lower purity, but useful as a fluxing material in glass 
making, is found in large quantities at Pasay Beach, Rizal Prov- 
