226 The Philippine Journal of Science wu 



of tons, lie near the foot of the slope. They are ranged over 

 a distance of about 300 meters along a northeast line, which is 

 continued farther in both directions by bowlders of iron-stained 

 quartz. The ore bowlders lie on the surface embedded in re- 

 sidual clay, and no ore in place is to be seen. The rocks exposed 

 in the stream adjacent to the bowlder ore include small areas of 

 the granite, which is complexly distributed among altered fel- 

 sitic tuffs and flows, and intrusive rocks which penetrate both 

 granite and effusives. Limestone overlying quartz-sandstone 

 and conglomerate is found close by, both to the east and west of 

 the ore, and bowlders of limestone are mingled with the bowlders 

 of ore. No replacement of limestone by iron ore, like that at 

 Camaching, was detected at Santol; in a general way, the lime- 

 stone bowlders occupy a position just above the ore bowlders 

 on the hill slope. 



It is not apparent whether the limestone east of Santol is the 

 Binangonan limestone with which the limestone to the west of 

 the deposit is correlated or whether it is the lower limestone. 

 The dip of the beds is uniformly to the west in both exposures, 

 and both limestones are much jointed; they are alike indistinctly 

 bedded, yellow to white in color, and in large part crystalline. 

 Faulting along the strike might have displaced the Binangonan 

 limestone in such a manner as to make it appear at apparently 

 different stratigraphic horizons on the two sides of the ore 

 deposit. 



In the limestone which lies to the east of the ore, a very white 

 crystalline bed was observed, samples of which upon analysis 

 proved to be dolomite. Dolomite is of unusual occurrence in the 

 Philippines, and it seems probable that its occurrence here is the 

 result of the replacement or dolomitization of original limestone. 

 An origin related to that of the ores is suggested by the fact 

 that most of the ores carry an unusually large content of mag- 

 nesium as compared with their calcium content. 



MINOR ORE DEPOSITS 



At Tumotulo, 3 kilometers southwest of Santol, an insignificant 

 quantity of ore was observed as small bowlders of hematite which 

 occur together with similar bowlders of porphyritic andesite 

 half way up the eastern wall of the valley of Bay abas River. 

 The hillside on which the bowlders are found consists of shales 

 and sandstone overlain at the top of the hill by the Binangonan 

 limestone. The ore is massive hematite with some magnetite, 

 quartz, and pyrite. Chemical analysis reveals the presence of 

 9.31 per cent of titanium oxide in this ore, whereas no other 



