216 GEOLOGICAL RECONNAISSANCE OF THE DOMINICAN REPUBLIC. 



lower part. The thickness of the part of the gypseous strata that con- 

 tains the salt is about 50 meters, but further development would perhaps 

 show a greater thickness and the presence of other salt-bearing strata. 



The salt is found in lenticular masses. The pits have been dug to 

 shallow depths in an unsystematic way and no lenses have been com- 

 pletely exposed. The thickness of the lenses ranges from a few centi- 

 meters to 6 meters and perhaps more, but in none of the excavations has any 

 attempt been made to discover their length. Probably few of the lenses 

 are much over 20 to 30 meters long and most of them are shorter. The 

 three principal sets of workings of the Commune of La Salina are rather 

 far apart but were probably located in a haphazard way, for salt is found 

 at several places between these workings. Although individual lenses are 

 short, the deposits probably are fairly continuous throughout the length of 

 the Cerros de Sal. The salt in the lenses is massive, and nearly all of it is 

 white. Layers of red and of black or nearly black salt are reported but 

 are not common. Large, white, semitransparent crystals of halite, some 

 of which are nearly a meter long, are found rather frequently. The green, 

 soft shale associated with the lenses is distinctly saline in taste for con- 

 siderable distances from the masses of salt. 



The easternmost of the principal workings is Carrera del Potro, where 

 only one opening has been made. The salt exposed is a lens nearly 6 meters 

 thick, banded with ribbons of green shale, most of which are only one or 

 two centimeters thick. These ribbons are somewhat wavy but are in 

 general vertical, thus agreeing in dip with the lens. The strike is N. 85° W. 

 East of this opening, on the line of strike, is an outcrop of gypsum and west 

 of it is shale. 



The Manuel Perez excavations are more than a kilometer west of Carrera 

 del Potro. Here a number of pits are scattered over an area roughly 50 

 meters wide by 300 to 400 meters long. There are nearly a score of exca- 

 vations in this area, all of which are small and shallow. The lenses of salt 

 range in thickness from a few centimeters to more than a meter. Some 

 are close together and even merge into one another. They lie in the usual 

 green to yellow shale. At this locality work was in progress at the time of 

 the visit. 



The Partilla workings, which are about as far west of the Manuel Perez 

 locality as Carrera del Potro is east of it, are similar to those at the Manuel 

 Perez. The excavations are perhaps fewer, but are deeper, and the 

 average thickness of the salt lens exposed is a little greater. The salt here 

 has a more greenish cast than elsewhere, probably due to admixed clay. 



The rock salt in Cerros de Sal is so good that it is used for some purposes 

 without refining. Salt picked clean of shale will probably average about 

 90 per cent of sodium chloride. The results of analyses of 12 samples 

 from Cerros de Sal are given in the accompanying table. The impuri- 



