344 



The Philippine Journal of Science 



1915 



3 to 6 meters of ore; 21.9 per cent encountered from 6 to 9 

 meters of ore; 6.8 per cent encountered from 9 to 12 meters 

 of ore; and 1.4 per cent encountered from 12 to 15 meters of 

 ore. The analyses indicate that a few of the holes did not 

 penetrate to the underlying parent rock. On the other hand, 

 some of them went into the parent rock farther than mining 

 operations would extend. Hence, these two possible sources of 

 error in the determination of the average depth tend to balance 

 each other. The holes were always continued until they struck 

 hard rock, and usually represent the actual thickness of the 

 surrounding ore. 



Of the drill holes located in poor areas, 29.4 per cent encoun- 

 tered no ore ; 58.8 per cent encountered from 0.5 to 3 meters of 

 ore; 5.9 per cent encountered from 3 to 6 meters of ore; and 

 5.9 per cent encountered from 6 to 9 meters of ore. 



Specific gravity determinations on small pieces of the ore in- 

 dicate that its dry weight in place must be from 1.7 to 2.5 

 metric tons per cubic meter. This estimated unit weight may 

 appear to be low for an iron ore, but as a matter of fact the 

 Surigao ore is very porous. In the following estimates it will 

 be assumed that 1 cubic meter of dry ore weighs 2 metric tons. 



According to these figures the areas of good ore contain 

 275,400,000 metric tons of ore as follows: 



Table III. — Quantity of ore in good areas. 



Average depth (meters). 



Quantity. 



Cubic me- 

 ters. 



Metric tons. 



1.76 . .- - 



15,100,000 

 46, 300, 000 

 49,200,000 

 21,400,000 

 6, 700, 000 



30,200,000 

 92, 600, 000 

 98, 400, 000 

 42, 800, 000 

 11,400,000 



4.50 



7.50 . . 



10.50 - . . — — - 



13.60 .. . . . . . 



Total _.. — _. 



137, 700. 000 



276. 400. 000 





If it be assumed that only areas over which the average depth 

 is 3 meters or more can be exploited economically, the total 

 available tonnage becomes 260,300,000. One half of this quan- 

 tity, or 130,150,000, is fairly accessible from Dahikan Bay as 

 a base. 



The quantity of ore included in the area classed as poor 

 is 222,400,000 tons, as follows: 



