334 COX, REIBLING, AND REYES. 
Binangonan limestone is the more available to Manila because 
of the more difficult water transportation or the expense of the 
necessary railroad transportation from Montalban to Manila. 
In either place there is an abundant supply of almost pure 
limestone within 30 kilometers of Manila. 
The siliceous materials in the vicinity of Manila vary greatly 
in chemical and physical properties, but after careful considera- 
tion we were able to select 8, so that the variety included the 
principal characteristics of all of probable importance. Their 
character and usefulness will be discussed in conjunction with 
their location. 
Beach sand.—South of Manila there is no stream entering the 
Bay which contains deposits of sand. Between 12 and 14 kilo- 
meters from Manila at Sangley Point and at Las Pinas, with 
which there is water communication, beach sand is abundant. 
This sand is derived principally from basaltic rocks which occur 
fragmentally in the tuff formation which borders Manila Bay. 
The grains are in an advanced stage of decomposition and are 
easily crushed. The Manila beach itself at Maytubig has similar, 
but very fine, sand from which fairly good sand-lime bricks have 
been manufactured. The efficiency of this fine beach sand is 
of more than ordinary importance because it is the only available 
siliceous material which is fine enough to require no grinding, 
and also because it is so abundant and easily procured. This 
work was completed before property owners near Maytubig pro- 
tested against the removal of sand. Now a supply will have 
to be obtained from a greater distance or dredged from the bay. 
TABLE VII.—Maytubig beach sand and its efficiency as a sand-lime brick 
material. 
Content of silica (SiOz). 
| | 
Description and classification. Some Soluble i in| ree 
chloric sodium | silica or ra 
carbonate 
(aaa) | @Na2C0s).| MF 
A very fine-grained sand containing magnetite, con- 
siderable partly kaolinized feldspar, and a little 
quartz. The grains of magnetite, pyroxene, and | 
hornblende are generally rounded, and those of | 
feldspar and quartz angular--_-__--------------------_-- 0.37 | 14. 86 2.61 | 60.51 
| 
Per cent.| Per cent. | Per cent.| Per cent. / 
