56 ANNALS NEW YORK ACADEMY OF SGTENCES 



There are many surface bowlders of magnetic iron of fine quality in 

 this vicinity, A little "imdergrouncl working is evident at one point but 

 this is now caved in. Surface observations, together with a few magnetic 

 observations, failed to show any very extensive deposit at that point, but 

 the quality appears to l3e good in iron content. The ore carries a little 

 copper and is associated with an igneous rock essentially andesitic in 

 composition. It could be traced with a fair degree of certaint}^ abont 

 fifty feet east and west just below the crest of the ridge. Considering the 

 associations at this place, it seems necessary to conclude that the ore is 

 igneous in origin and that it probably accompanies one of the porphyrite 

 intrusives. Other occurrences of similar ores were mentioned to us in 

 this same region, but none were visited. 



Coal and Oil 



There is no good ground for believing that valuable resources of these 

 products exist in Porto Eico. Some prospecting for them is carried on, 

 however, in a desultory way. The only basis for the hope of finding coal 

 is the occurrence of lignite and lignitic material with the shales lying at 

 the base of the younger series of rock formations, below the Arecibo lime- 

 stone member. Lignitic material was seen in these shales near Lares, 

 and similar or better material has been reported from near San Sebas- 

 tian. From what has been seen, there seems to be no promise of very 

 valuable deposits of this kind. The structure is simple and a very little 

 exploratory work done in a systematic manner would determine the prob- 

 able value of every occurrence known. There is no promise at all of such 

 content in the older series. 



No oil indications were observed. The only formation to be considered 

 in investigating the prospect of oil is also the basal shales of the younger 

 series. 



Lim erode 



A particularly porous, granular and uniform limerock is obtained from 

 the small island. Icacos, just off the northeast coast, and is used in sugar 

 refining at the Central, owned by the Bird brothers, at Fajardo. The rock 

 is organic, largely foraminiferal, and is probably structurally of the same 

 origin as the San Juan dune sand deposits, — comparatively recent. Such 

 materials are doubtless to be found in large amount, but not always so 

 pure and so uniform in quality and structure. Limestone suitable for 

 lime burning or for cement mixture is certainly not rare. Limestone of 

 a quality that would permit its use in structural work is also found at 

 some places, but apparently very little native stone is used. 



