X, A, 5 Pratt: Iron Ore on Calambayanga Island 325 



north, in the construction of a short breakwater, it would be 

 possible to make a small secure harbor at this point with no 

 great expenditure. Dahikan Bay, 4 kilometers (2.5 miles) to 

 the east of Calambayanga Island, is charted as a safe anchorage 

 by the Coast and Geodetic Survey. 



Fresh water is to be had only in limited quantity on the 

 island itself, but could be obtained in abundance on the adjacent 

 mainland. There are several small springs on the island, and 

 in the rainy season these give rise to a small stream. 



HISTORY 



Concessions for iron mines on Calambayanga Island were 

 sought repeatedly during the Spanish control of the Philippine 

 Islands, but there is no record that any was granted. The iron 

 ores in the Eastern Cordillera of Luzon were known and ex- 

 ploited in the seventeenth century, and probably the deposit on 

 Calambayanga Island was discovered at a similarly early date. 

 It is probable that Filipino iron smelters were operated at the 

 Calambayanga deposit, as they have been in Bulacan Province, 

 since pieces of slag and inclosed charcoal much like the Bulacan 

 slags have been found near Mambulao by Mr. A. C. Cavender, 

 the present owner of the Calambayanga ores. 



GENERAL GEOLOGY 



The Calambayanga iron ore lies at the western border of the 

 Paracale gold field, which has been productive for three cen- 

 turies and at present yields nearly 50 per cent of the total gold 

 production of the Philippines. The gold appears to be associated 

 with granite, which is intruded into more basic rocks — diorite 

 and peridotite; the gold is found in veins which formed in the 

 granite and the surrounding rocks after the solidification of 

 the intrusion. To the west and southwest of and overlying the 

 granite and diorite area is a series of sedimentary rocks younger 

 than the granite and probably of Miocene age. The iron ore 

 is found in the base of these sedimentaries, which include sand- 

 stones, conglomerates, shales, tuffs, and minor limestones. 

 All the rocks in the district have been metamorphosed by re- 

 gional dynamic action, and the sedimentary rocks have been 

 pierced by dikes and overspread by flows and agglomerates. 

 Probably the dynamism which rendered the granite gneissic 

 and the diorite schistose over the whole district and indurated, 

 folded, and faulted the sedimentary beds was accompanied or 

 followed by the extrusions, which are andesite. The fractures 



