GEOLOGIC RECONNAISSANCE OF SOUTHWESTERN LUZON. Ill 



Calamba to Los Baiios was constructed. The rock, which is an andesite, 

 is exposed in a high face, and the quality was found to be satisfactory. 



Limestone. — -Limestone from east of Montalban has been cut and po- 

 lished for the base of columns in some of the churches in Manila and has 

 been used for floors, sidewalks, and for paving patios. 



GEAVEL. 



A large amount of gravel is dredged from the Pasig and Mariquina 

 Elvers for use in concrete construction, surfacing roads and filling low 

 areas. It is of fair quality and makes a good substitute for crushed 

 stone in concrete work, although it is not so evenly graded, and will not 

 stand so great a compression stress. 



Beach gravels and bowlders have been transported from the mouth of 

 the Pinamucan Biver, on Batangas Bay, to the town of Batangas, where 

 they were crushed and used in constructing the macadamized roads 

 leading to Bauan and San Jose. The bowlders are andesite and have 

 suffered considerable disintegration by the action of water, so that the 

 crushed stone from them is not as good as would be obtained from a 

 quarry of the same rock. 



SAND. 



Sand for use in Manila has been principally obtained from the Pasig 

 Biver by diving and dipping it up in baskets and by dredging. During 

 the field work which was done for this report, a large deposit of sand 

 was found in the Orani Biver, which is navigable for launches. It is 

 of superior quality and some of it is now being used in Manila. 



Sand has also been obtained from Sangley Point near Cavite, but it is 

 of inferior quality. In building the fortifications near the entrance to 

 Manila Bay, beach sand consisting largely of fragments of shells has 

 been used. There are many places where sand is available, and in build- 

 ing concrete bridges and public buildings it is customary to use a local 

 supply. The sources above mentioned are the only ones from which 

 large quantities have been obtained. 



CLAY AND CLAY PRODUCTS. 



A fair quality of kaolin has been obtained for many years from 

 deposits situated on the lower slopes of Mount Maquiling, near Los 

 Banos. It is used in making whitewash. It has evidently been formed 

 by the disintegration of rocks through solfataric action, since there are 

 small solfataras and hot springs near the deposits. A similar kaolin has 

 also been worked near Matiquio on the east side of Jalajala Peninsula 

 and in a small way to the east of Nasugbu. Within the tuff area there 

 are some deposits of fine-grained clays interstratified with the tuff beds 

 and occurring in more or less lenticular masses. One of these which has 



