IX, A, 3 Dalburg and Pratt: Iron Ores of Bulacan 227 



ore analyzed contained more than a small fraction of 1 per cent 

 of this constituent. 



Smelting furnaces have been operated at Macatalinga, Mayapo, 

 and at Tagpis 6 to 10 kilometers east of Hison, but very little 

 ore is to be seen at any of these places. The country is made 

 up of effusive rocks much silicified. The ore is hematite, often 

 of the specular variety, with pyrite and quartz. It is found 

 sparingly in small detached pieces on the surface of, or- embedded 

 in, residual clay near the summit of the divide between Bayabas 

 and Angat Rivers. 



CHEMICAL COMPOSITION OF THE IRON ORE 



The ore used for smelting charges in Bulacan Province usually 

 carries more than 60 per cent of metallic iron, and samples 

 secured by breaking up bowlders usually carry nearly or quite 

 as high a proportion of iron. Smelting charges as employed 

 by the Filipino, however, represent selected ore especially in 

 the elimination of all quartz-bearing material, and it is probable 

 that surface bowlders are also richer in iron than a repre- 

 sentative sample of the ore in place would be. Therefore, it 

 may be expected that the deposits entire carry somewhat less 

 iron than the ore which it is possible to sample at present. 



The analyses in Table I show the chemical composition of 

 samples from each of the ore bodies discussed. For convenient 

 comparison, analysis of an ore from Hongkong and analyses of 

 several standard iron ores have been inserted. 



The analyses show that the ores smelted are fairly pure mag- 

 netites or hematite or a mixture of these two minerals; in 

 all cases the combined water is very low. Except in the 

 quartzose ore, alumina is high in proportion to silica as com- 

 pared with the iron ores most widely smelted elsewhere. Mag- 

 nesia is generally more abundant than lime. A majority of the 

 ores are vv^ithin the Bessemer limit as to phosphorus, although 

 some exceed it. Sulphur is reasonably low in the pure ore, 

 but is high in the replaced wall rock where it occurs as pyrite. 

 Pyrite from Montamorong was found to contain 0.15 per cent 

 of cobalt, and it is probably due to traces of cobalt in the 

 pyrite generally that slags from all the furnaces show a cobalt- 

 blue color in patches. Titanium and manganese are low with 

 the exception of the one ore from Tumotulo which is inexplicably 

 high in titanium. In the quartzose ores, silica increases at the 

 expense of the iron, while in the altered wall rock it is probable 

 that magnesium, aluminum, and lime replace the iron, although 

 no analysis of this material was made. 



