ECONOMIC GEOLOGY. 229 



the sea and from large towns, so that transportation involves difficult 

 problems, but good wagon roads or even railroads could easily be con- 

 structed. 



This report is based on observations made by Wythe Cooke and the 

 writer in April, 1919, during a rapid reconnaissance of some of the more 

 accessible deposits. The limitations of time prohibited a thorough exami- 

 nation or prospecting for other deposits. 



MAGNETITE DEPOSITS NEAR HATILLO. 



Prospectors have dug shallow pits in the red clayey soil of the limestone 

 hill a little north of west of Hatillo, at the border of the savanna on which 

 the settlement is built. The soil in these pits, most of which are near 

 the summit of the hill, contain subangular blocks of massive magnetite, 

 20 to 25 centimeters wide. In the bottom of one pit is a mass of magnetite 

 that is firmly embedded but probably is not in place. The limestone, 

 which outcrops at many places on the hill, contains a little rusted pyrite, 

 but no magnetite was observed at the outcrops. Similar deposits of mag- 

 netite are reported at other localities near Hatillo. 



Veinlets of quartz and calcite that run parallel to the apparent bedding 

 were observed in the limestone of a similar hill south of Hatillo, where the 

 exposures are better. As some of the limestone is partially marmorized, 

 it probably has been subjected to mild contact metamorphism. As stated 

 on page 60, this limestone is believed to be of Eocene age, but this belief 

 is based principally on the lithology. 



About 3 kilometers northwest of Hatillo, on the opposite side of Rio 

 Yuna, H. G. Ferguson, of the United States Geological Survey, found a 

 similar deposit of magnetite associated with limestone. He noted slate 

 jnterbedded with and above the limestone and siliceous, schistose porphyry 

 on the trail north of the magnetite deposits. Fine-grained porphyries of 

 various types were seen during the present investigation some distance 

 north of Hatillo but none were observed near the magnetite deposit that 

 was examined. 



The origin of the magnetite in this locality is uncertain. The boulders 

 of magnetite are probably small masses that were originally in the limestone 

 or at the contact of the limestone and porphyry and are now enclosed in the 

 residual soil produced by the decomposition of the limestone. This view 

 is strengthened by Ferguson's discovery of igneous rock near one of the 

 known occurrences of magnetite and by our discovery of recrystallized 

 limestone south of Hatillo. Megascopically the magnetite appears to be 

 sufficiently pure to be a high-grade ore. Analysis of a sample collected 

 by Ferguson gave the following results: Fe, 66.35 per cent; P, 0.75 per 

 cent; Si0 2 , 2.44 per cent. 



