RECONNAISSANCE OF MINDANAO AND SULU : III. (389 



The Tubay Eiver above the junction with the Asiga is as smooth as 

 a pond and has scarcely any current. Gravel from below the jmiction, 

 whether taken from the banks or from the river bed, gave three to eight 

 colors to every pan. The gold is evidently brought down by the Asiga, 

 the source of which lies east of Lake Mainit, and on the western slopes 

 of the long mountain range extending from Surigao on the north to 

 Cape San Agustin on the south. Numerous hornblende diorite boulders 

 were observed in the Asiga, many of them heavily impregnated with iron 

 and copper pyrites implying generous mineralization of the country 

 traversed by this river. I believe that the region about the headwaters 

 of the Asiga might well repay further prospecting for both copper and 

 gold. 



The banks of the Tubay Eiver consist of metamorphic rocks, mostly 

 chloritic schists. A finely laminated mica schist containing a large 

 percentage of calcite (calc-schist) is also very abundant. 



About six kilometers northeast of Santiago on the Tagbunuan Creek 

 is an outcrop of a dark greenish sandstone, the basic fragments of which 

 are very much weathered and serpentinized. The banks are very steep 

 at this point and have recently slid, covering the ground with a great 

 mass of debris, but exposing in the solid formation several minute seams 

 of coal, none of them more than one centimeter in thickness. The super- 

 stitious natives prize these black fragments for the medicinal properties 

 they are supposed to possess. As I neither saw nor heard of any speci- 

 mens larger than a walnut, I presume that no thicker seams than those 

 I observed outcrop anywhere in the neighborhood, and this occurrence of 

 coal therefore has no economic value. 



The effects of regional metamorphism are well shown, not only by the 

 folding and fracturing of the minute coal seams, but by the chemical 

 composition of the coal itself. An analysis of the fragments showed the 

 following composition : 



Per cent. 

 Water 8.10 



Volatile combustible matter 22.95 



Fixed carbon 55.29 



Ash 13.66 



Total 100.00 



As compared with other Philippine coals, the percentage of water is 

 somewhat lower, and that of ash somewhat higher than the average, but 

 the greatest difference lies in the high ratio of fixed carbon to volatile 

 constituents. The loss in volatile constituents with the corresponding 

 increase in fixed carbon evidently is due to the intense pressure, accom- 

 panied no doubt by considerable heat, attendant upon the dynamic stresses 

 engendered by the folding of the rock strata during some recent period. 

 Further evidence of this metamorphism will be referred to later. 



