224 



The Philippine Journal of Science 



1914 



area, and within a few meters farther east sedimentary rocks 

 are found. The general relations for the Hison outcrop are 

 shown in fig. 6. The granite in the immediate vicinity of the 

 ore bodies exhibits the recemented border zone noted in the 

 description of the granite, and is cut by dikes of both acidic 

 and basic character. Some of these dikes strike parallel to the 

 trend of the ore, that is, north 15° east, but dikes striking in 

 various directions were noted. 



A green felsite which has the appearance of a fine-grained, 

 altered tuff occurs with the sedimentary rocks east of the out- 

 crop. Smith examined several thin sections of this rock, and 

 concluded that it was fragmental in character, altered, and 

 somewhat schistose; the sections contained fragments of quartz 

 and feldspar in a mat of minerals of the chlorite group, together 

 with considerable magnetite. This rock grades into the usual 



Fig. 6. Geologic section through ore body at Hison, along an east-west line ; diagrammatic in 

 part: (o) Granite; (6) intrusives ; (c) altered wall rock; (d) iron ore; (e) effusives ; 

 (/) limestone, shale, and sandstone: length of section, about 200 meters. 



type of wall rock at the outcrops proper. The sedimentaries 

 consist of schistose, black, laminated shale; schistose, mottled 

 gray limestone in beds made up of thin lenses; and a clayey 

 sandstone-conglomerate or clastic. The strata strike north 15° 

 east; the dip is uniformly to the east at a high angle, but the 

 structure is evidently that of a closely folded or flattened syn- 

 cline. The total thickness of the sedimentaries as exposed in 

 Maon Creek is apparently not more than 50 meters. 



At Hison, ore has been dug out of the bank of a small creek 

 called Sapang Bacal (Iron Creek), until a face several meters in 

 height above the bed of the stream is exposed. A wall trending 

 north 20° east extends along the west side of the ore pit; it 

 consists of the usual green silicate minerals with magnetite, 

 quartz, and pyrite. The floor of the excavation over an area of 

 about 50 square meters and one face, some 5 meters in width, are 

 soft massive magnetite. On the surface above and south of the 

 ore face are large, hard bowlders of hematite with magnetite. In 



