156 The Philippine Journal of Science 1914 



varied more widely than these two in composition. The chalk 

 at the second quarry site is more uniform, and the composition 

 of every sample taken from this site is very close to that of 

 37 or 39. The material at both sites is closely similar to a 

 raw mixture for Portland cement in composition ; the f ragmental 

 coralline limestone contains from 10 to 14 per cent of silica 

 and from 3 to 5 per cent of iron and aluminum oxides, while 

 the chalky limestone contains from 7 to 9 per cent of silica 

 and about 3 per cent of iron and aluminum oxides. Neither 

 material contains more than 1 per cent of magnesia. 



Something of the relative ease of quarrying these limestones 

 is to be inferred from the experience of the district engineer 

 at Cebu. Such rocks have been classed as "soft rock excavation" 

 in the specifications for practically all engineering work involv- 

 ing excavation in them. Contractors have found it advantageous 

 in several cases to remove such material by pick and shovel 

 without the use of powder. In Portland cement manufacture the 

 coarse crushing of these materials should also be accomplished 

 cheaply because of their softness and naturally fine grain. 

 The cost of fine grinding, on the other hand, might be slightly 

 higher than usual since chalk is less brittle than the crystalline 

 limestones which are commonly used in making Portland cement. 



Calcareous material ^6. — Sample 46 represents a bedded, 

 crystalline limestone which outcrops in the western base of 

 Mount Magdagoog on Pandan River about 2 kilometers from 

 the coast. This limestone is stratigraphically lower than the 

 rocks just described, and between it and the chalky limestone 

 some 50 meters of calcareous sandy clay and a considerably 

 greater thickness of volcanic agglomerates intervene. The 

 agglomerate forms the core of Magdagoog Range, and is exposed 

 in the caiion of Pandan River. Limestone 46 appears to stand 

 on edge in the most clearly defined exposures, and the strata 

 are much broken. 



In composition, 46 is a fairly pure limestone; the ratio of 

 silica (3.1 per cent) to iron and aluminum oxides (2.2 per cent) 

 is less than in the more readily available limestones near the 

 coast. The small number of samples which have been taken 

 show moderate uniformity in chemical composition. The lime- 

 stone is available in an adequate quantity, and is encountered 

 along the route of the proposed railroad from the mill site 

 to the Uling coal field, as are all the other materials considered. 



Calcareous material 50. — Sample 50 is a crystalline and 

 relatively pure limestone, which is interbedded in the base of 

 the coal measures and lies inland about 7 kilometers from the 



