100 The Philippine Journal of Science mi 



honeycomb), manganese, and iron oxide. It presents a marked 

 ribbon or banded appearance from the alternating layers of 

 different classes of ore. This banding is generally parallel to 

 the walls, but occasionally is seen in concentric rings. Numer- 

 ous irregularities occur in the dip and strike of the vein, and 

 horses are frequently encountered. The vein is from 3 to 6 

 meters wide, and can be traced for several hundred meters along 

 the outcrop. 



Eastern group. — There are several parallel veins in this 

 group. The two principal ones are the Nancy No. 1 and the 

 Nancy No. 2. 



The Nancy No. 1 is a quartz-calcite-manganese vein from 4 to 

 6 meters wide. In the upper workings massive quartz predom- 

 inates, but in depth practically the whole vein is calcite. 



The Nancy No. 2 vein is in places only 3 meters from the 

 Nancy No. 1. This distance varies greatly, owing to the varia- 

 tions in dip and strike in sections of the two veins. The vein 

 is practically all calcite, although in places it contains a little 

 quartz and manganese. It varies in width from 6 to 20 meters. 

 It is low grade except along certain lines of enrichment 1 to 3 

 meters wide. 



Keystone mine. — This property is located on Aroroy Mountain 

 at the northern part of the district. The vein-filling is quartz 

 (somewhat honeycomb), iron oxide, and small amounts of 

 manganese. The quartz is much shattered, and is cut by numer- 

 ous stringers of quartz deposited at a later period. 



PLACER DEPOSITS 



The natural result of the weathering and erosion of a country 

 containing numerous gold-bearing veins, as represented by 

 Suyoc, Baguio, Lubang, Paracale, and Masbate, is the formation 

 of placer deposits. Beside these localities, gold-bearing placers 

 have been found in several regions where quartz prospecting has 

 been carried on to a very limited extent and consequently com- 

 paratively few veins have been discovered, as in Nueva Ecija, 

 Tayabas, Catanduanes, Mindoro, Mindanao, and other places. 

 The localities from which placer gold has been reported are 

 shown in fig. 4. 



For the most part, placers are found in the valleys of the 

 modern drainage system, but at least two cases have been discov- 

 ered where the deposit was the result of ancient erosion. The 

 best example of the latter class is the Cansuran deposit, Surigao, 

 Mindanao. 



