230 GEOLOGICAL RECONNAISSANCE OF THE DOMINICAN REPUBLIC. 



Brinsmade, 1 in his report on this district, mentions four localities at 

 which he found similar magnetite deposits besides the one here described. 

 He gives six analyses, which show that the magnetite is of high quality 

 and that the ore is a mixture of hematite and magnetite, with a larger per- 

 centage of the hematite than is evident from field examination. He 

 thinks that the material in which the magnetite is embedded is decomposed 

 porphyry. 



The magnetite deposits of this district have no present commercial value, 

 for the amount exposed in the pits is entirely too small to warrant exploita- 

 tion. A magnetic survey of all areas in this district where limestone out- 

 crops or is supposed to occur is desirable to ascertain whether there are 

 larger lenses of magentite. 



COPPER DEPOSITS NEAR HATILLO. 



Copper prospecting has been carried on intermittently for many years in 

 the vicinity of Hatillo. The known indications of copper are on Loma de 

 la Mina, about 4 kilometers southeast of Hatillo. Many small prospect 

 pits have been sunk on this mountain and at one place, near the summit, 

 there are large workings consisting of shallow trenches and pits. The 

 main dump, which is on the side of the mountain, is about 75 meters in 

 diameter and has a maximum depth of about 25 meters. A little ore was 

 evidently smelted by some of the prospectors. Several hundred meters 

 south of the main workings there are some small pits, and on the surface 

 of the ground nearby there are pieces of slag, some of which contain blebs 

 of metallic copper. 



In the pits where the ore was smelted there is a small quantity of bog 

 iron ore mixed with lignitic material consisting of partly carbonized seeds 

 and other vegetable matter. The bog iron ore has formed since the pits 

 were dug. These deposits are of no commercial value, but they are of 

 interest as showing the rapidity with which bog iron ore can be formed. 



Loma de la Mina is composed principally of chloritic schist. Near its 

 base gneissic igneous rock, probably dioritic, was observed in places. 

 The mountain is covered with a rather thick mantle of soil and outcrops 

 are not abundant. 



The principal workings are on a shear zone in chloritic schist, which has 

 been much crushed and sericitized. The schist is locally stained with iron 

 and bears scattered copper stains. It contains a few small quartz stringers, 

 but most of them are only a centimeter or two wide. Some of the stringers 

 contain a little azurite, but most of them are barren. A few fragments of 

 hard gossan were seen. A small amount of a mineral that is believed to be 

 alunite and a little chalcanthite were found in the schist. 



These deposits are so inaccessible and the quantity of copper they con- 

 tain in so small that they are of no present commercial value. 



1 Brinsmade, Robert B., Iron in Santo Domingo: Mining and Scientific Press, vol. 117, pp. 356-358, 

 Sept. 4, 1918. 



