vin, a, 2 Edding field: Ores of the Philippines 91 



So far as development has gone at the present time, no second- 

 ary zone of secondary enrichment has been found in copper-free 

 veins, which tends to strengthen the assumption that enrichment 

 has been accomplished mechanically. In practically all cases the 

 richest ore is found near the surface, and the values found so 

 far appear to decrease with depth until the unaltered ore is 

 reached. 



The following table gives the principal gold-bearing veins in 

 the Philippines with their chief characteristics. 



