IX, A, 2 Pratt: Geology of Cement Materials 157 



coast along Pandan River. It contains numerous foraminifera, 

 and is referred by Smith ^ to the Oligocene. The limestone is 

 bedded, with a total thickness of some 10 meters, and dips 

 at a high angle to the west. As in the case of limestone 46, 

 it has not been thoroughly sampled but appears to be fairly 

 uniform in composition with about 2.0 per cent of silica and 

 1.5 per cent of iron and aluminum oxides as the principal 

 impurities. Although it is at a considerable distance from the 

 coast and the cost of quarrying would be high on account both 

 of the hardness of the rock and the limited width over which 

 the quarry face could be extended because of the steep dip 

 of the beds (fig. 2), limestone 50 can be obtained in adequate 

 quantity and is therefore considered as an available calcareous 

 raw material. 



The upper limestone in the coal measures which occurs at 

 an elevation of from 550 to 650 meters on Mount Uling, on 

 the other hand, is so far from any railroad that would be built 

 to bring the coal down to the coast that it may be considered 

 inaccessible and therefore not available for cement manufacture. 



Siliceous material U7. — Sample 47 represents an extensive and 

 exceedingly regular formation made up of very fine volcanic 

 tuif or ash which is indurated into a moderately hard, light- 

 colored rock of fine grain and splintery conchoidal fracture. 

 Bedding planes are not clearly defined, but numerous minor 

 joints pass through it. 



The tuff lies stratigraphically below ■" limestone 46 and in 

 close proximity to the andesitic agglomerate in Magdagoog 

 Range ; underlying it in turn are the shales, sands, and conglom- 



' Doctor Smith studied thin sections of this rock, and his notes indicate 

 that the conspicuous fossil casts in it are very similar to, if not identical 

 with, Heterostegina margaritata, which according to L. Schlumberger 

 [Note sur un Lepidocyclina nouveau de Borneo in Santm. d. geol. Reichs- 

 mus. in Leiden (1902), I, 6, pt. 3] was found by K. Martin in the Oligo- 

 cene at Dax (France ?). 



" It is not clear whether the tuff is related in origin to the andesitic 

 agglomerate in Magdagoog Range or not. In fact, there is doubt as to the 

 relative age and the manner of origin of the agglomerate which is breccia- 

 like in some exposures and appears to surround or inclose a core of massive 

 andesite. The apparent metamorphism and disturbance in the crystalline 

 character and upturned beds of limestone 46 and in the indurated, closely 

 jointed structure of the tuff could be explained by assuming that the andesite 

 was of intrusive origin and had forced itself up through these rocks subse- 

 quent to their deposition. Evidence of local thermal action may be deduced 

 from the presence of hot mineralized springs in the andesite at the barrio 

 of Mainit. Apparently the andesite may have resulted from volcanic 

 activity which yielded alternately flows and coarsely fragmental ejecta at a 



