RECONNAISSANCE OP SOUTHEASTERN LUZON.' 461 



a thickness of a little more than a meter, it probably can not be mined 

 commercially. 



It was reported that marble is found on the coast a short distance 

 west of Matnog, but the place was not examined. It may be that there 

 are some raised coral reefs in this viciaity. Limestone was reported 

 as occurring near Castilla on the north shore of the entrance to Sor- 

 sogon Bay. An examhiation of the locality which is near the iarrio 

 of Libtong resulted in finding some raised coral beaches. 



Formation of the Paracale-Mamlulao mineral district. — Von Drasche 

 mapped this district a.s older crystallines, gneiss, chlorite-hornblende- 

 schist, etc. 



lekis, who described the district but did not attempt any mapping, stated 

 that in a general way it may be said to consist of hornblende diorite, schist, 

 and gneiss. He writes that Mount Bagacay is composed of diorite porphyry and 

 that in the lower hills east of the Malaguit there is a light-colored hornblende 

 diorite. He also referred to the gneissic and schistose texture of the rocks at 

 various places. At the Tumbaga mine he found a rock having the appearance 

 of a slate. He also mentions an andesite as occurring at this mine. 



Smith in his report states that the formations found in the district are 

 pyroxenites, schists, granite gneiss, granite, shale, sandstone, and andesite, from 

 north to south in the order named. He says that the principal lodes to-day are 

 found along the granite-diorite contact and in the in-egular fractures in the 

 granite near its border. 



It may be that there ai'e contact ore deposits in the district, but in 

 so far as we have observed, the principal mineralization is in the veins 

 which are found in the granite and extending into the pyroxenite-peri- 

 dotite area.^ 



In the present report the formations are outlined in a simple man- 

 ner which it is believed will be helpful in the field to those who care to 

 study the general structure of the district. Moreover, it makes possible 

 a tentative discussion of the origin and relations of the ore deposits in 

 so far as now known. 



Along the coast there is an irregular belt of pp'oxenite with some 

 peridotites which in places are schistose. It extends from Mambulao 

 Bay beyond Paracale to Bagacay Point. These rocks usually are dark 

 colored and have a greenisli tinge, some of them being highly serpen- 

 tinized. The schists often are talcose and make the trails over the area 

 very slippery in places. 



Inland from the belt of country Just defined there is an area of 

 granite varying from massive to gneissic in texture.^ This rock consists 



* However, we did not examine all the undergi'ound workings in this area. 



* This rock and some others of the district were described by Joseph P. Iddinga 

 in The Petrography of Some Igneous Rocks of the Philippines. This Journal, 

 Sec. A (1910), 5, 1.55. 



106090 3 



