392 SMITH. 



between limestone on the west and basalt and andesite on the east. The 

 igneous rock has been largely disintegrated and the trail passes mostly 

 over a red residual clay which shows traces of large, weathered feldspar 

 phenocrysts of the andesite. 



A small community of Filipinos lives in the barrio of Tinabingan on 

 the west coast of the Bay of Placer. Tinabingan is known chiefly in 

 the Province of Surigao for its fonner activity in gold washing. Old 

 and abandoned tunnels, shafts, and ditches evidence the fact that this 

 industry at one time must have engaged a great number of people. To- 

 day, the only mining work done by the native population still remaining, 

 consists in the washing of the black sands on the beach. One American 

 miner lived at Tinabingan at the time of my visit there. Working ab- 

 solutely alone, and Avith biit small capital at his command, it is not at 

 all surprising that this one man could show but a very limited amount 

 of development, particularly so as he had been unfortunate in losing a 

 large j^art of his work as a result of slides and caves. 



The country rock of this region is andesite, intersected by a system 

 of veins, running in general about north 55° east and dipping 60° to 70° 

 toward the southeast. Many of these veins are mere quartz stringers less 

 than one centimeter in thickness. In general, the walls of these stringers 

 have become siliciiied to a greater or less extent, making the limits of the 

 mineralization very indefinite. 



About 7 kilometers northeast of Placer is the small island of Campiha, 

 where at one time comparatively extensive mining work was carried on. 

 The mouth of the main tunnel, about 5 meters wide and 10 meters long, 

 is found on the southern end of the island about 60 meters from the 

 beach. This tunnel is intersected by several short drifts, running in all 

 directions and at all inclinations, and now generally caved and in a 

 dangerous condition. The walls of the workings are mostly covered with 

 a clay gouge and no distinct vein could be observed anywhere. It is 

 possible that here, as in Tinabingan, the natives had discovered com- 

 paratively rich, but very narrow stringers of quartz and had followed 

 them until the values had disappeared, or else the abandonment was 

 caused by the flooding of the workings, for the floor of the main tunnel 

 is only about 3 meters above sea level, and the lower workings were 

 flooded at the time of my visit. Numerous samples were taken from 

 what appeared to be the most probable pay streaks, but the assay results 

 are so extremely low that the wonder is that even the natives could have 

 found this mining profitable or sufficiently encouraging to have done as 

 much work as they have. 



An old placer district, that has been worked by Spaniards and Fili- 

 pinos for a long, but an indefinite period of time, exists about 10 kilo- 

 meters south of the town of Surigao, at the head of the Cansuran and 

 Biga Creeks, both tributaries of the Surigao River. Many of the wealthier 



