76 ADAMS. 



McCaske) r , who made a reconnaissance of the region of the iron mines 

 near Angat, lays special stress on the fact that his observations justify 

 Von Drasche's mapping of the area as older crystallines, but he reported 

 finding fine-grained diorite, a granulite (quartz and feldspar with horn- 

 blende or mica), a gabbro, and a rose-red trachyte. He makes no 

 mention of gneisses or schists, and accordingly it is questionable if any 

 are to be found. 



The southern area of schists mapped by Von Drasche lies to the 

 southwest of Atimonan, and was seen by him in crossing from Laguimanoc 

 to Atimonan. He says, "On the eastern slope one finds finally a green 

 schistose chloritic talcose, but very decomposed rock, that in general 

 has ■ a steep dip to the eastward, while the tuff beds for the most part 

 dip to the southward." 



In crossing the eastern cordillera from Lucena via Pagbalao, to 

 Atimonan, a micaceous schist was found about 5 kilometers west of Ati- 

 monan. On the accompanying geologic map this outcrop is included 

 with Von Drasche's locality in a single area. The significance of these 

 schists is not clear, but it is quite possible that they are metamorphosed 

 Tertiary sediments. 



Diorites. — Within the area here discussed, the first locality mentioned 

 as containing older rocks is the region to the east of Montalban, where 

 the dam for the headworks of the water supply of Manila is now being 

 constructed in a gorge between two limestone cliffs on the San Mateo 

 River. In the literature, this is spoken of as the limestone cave region 

 of San Mateo, although it is distant from the latter place. Becker cites 

 Meyer as observing that the limestone in which the caves are found 

 rests upon diorite. Von Drasche, who visited the locality later, did not 

 describe such an occurrence, but he says: "The bowlders of this river 

 consist for the most part of older syenitic rocks, diorite, etc., and a 

 little trachyte." He described the relations of the limestones a short 

 distance to the north (Poray Creek), but made no mention of diorite 

 near it. In making the reconnaissance on which this report is based, 

 no diorite was found at the locality of the limestone. 



Itier says : "In Angat, at the base of the foothills of the cordillera of 

 Luzon, there exist no evidence of volcanic products and the rocks carried 

 by the river are. diorite, amygdaloid, spilite (amygdaloidal diabase), epi- 

 dote,. dolomite, porphyry . . ." 



Some of the streams of the eastern cordillera bring down diorite peb- 

 bles. Diorites are now known to occur in the region. At the iron 

 deposits on the Lanatin Eiver, worked by the Spanish and described later 

 in this report, the . writer found an area of diorite, a part of which is 

 within the drainage basin of the river that passes Montalban. Near the 

 area of schists west of Atimonan, dioritic rocks are exposed. No doubt 

 other areas' will be discovered when the country is thoroughly explored. 



