462 ADAMS AND PRATT. 



of white feldspar and quartz with dark green mica. It is exposed near 

 Mambulao and extends to Paracale and beyond to the Malaguit, in- 

 which stream there are some granite rocks forming very small islands. 



Bagacay Mountain consists of diorite. It forms the southern part of 

 the district and extends from near the coast, inland almost to the 

 mouth of the Daguit Eiver. The Labo Eiver flows for some distance 

 along its southern boundary. 



Inland from the granite ai'ea and north of the Bagacay diorite there 

 is a series of sedimentaries consisting of conglomerates, sandstones, 

 shales, and some limestone with intruded andesites. These rocks are 

 well exposed on the beach w^est of Mambulao and continue southward 

 to the Malaguit Eiver Valley. They are more or less metamorphosed. 

 A limestone of the series converted into marble was seen in the bed 

 of the Malapanay Eiver, a tributary of the Malaguit. 



These formations as defined are shown approximately on the accom- 

 panying geologic map. In using this classification it should be borne 

 in mind that the detailed structure and exact limits of the areas are not 

 yet known and that rocks from but relatively few localities have been 

 studied microscopically. 



The relative ages of the formation of the district have not been deter- 

 mined fully. The pyroxenites are older than the granite, since dikes 

 of the granite can be seen cutting the pyroxenites near Mambulao. 

 From the nature of the rock it vasij be inferred that the granite did 

 not originally appear at the surface, but has been uncovered by erosion. 

 The relations of the diorite of Bagacay are not clear, but this rock is 

 probably younger than the pyroxenite, since on the lower slopes of 

 Mount Bagacay there are places where the diorite seems to have been 

 intruded through the pyroxenite. The andesites intruded into the 

 Tertiary beds are younger than these sedimentaries, but it should not 

 be inferred that this is true of all the andesites of the region since 

 there is andesitic material in the conglomerate beds of the series. 

 Further conclusions as to the relative age of the formations can not 

 be made at this time. 



Ore deposits of the Paracale-Mamlulao mineral district. — The granite 

 is cut by many well mineralized quartz veins and a few of these can be 

 traced with a fair degree of certainty into the pyroxenites. At some 

 places where there are veins in the pyroxenite, the granite may occur 

 below. 



There are veins in the Bagacay diorite, but thus far no very important 

 ones have been found and they are not known to be continuous into 

 the other rocks. In the area of the sedimentaries and intruded ande- 

 sites there are a number of well defined veins, but they can not now 



