DIAMOND AND CAEBONADO WASHINGS IN BRAZIL. 219 



most of the escarpments and makes the topography extremely rough 

 and picturesque. 



The sandstone beds above the conglomerate are especially subject 

 to weathering and are at many places trenched by valleys, in whose 

 walls are exposed large surfaces of naked conglomerate. Thus along 

 almost all the eastern base of the mountains in the region between 

 Santa Isabel and Lencoes, over a distance of more than 60 kilometers, 

 the conglomerate covers almost the entire slope of the mountain, like 

 tiles on a slanting roof, and plunges with a dip of from 20° to 30° 

 toward the east into the bottom of the valle^^s of the Piabas, Chique- 

 Chique, Andarahy, and San Jose rivers that skirt the mountains 

 through this region, while the opposite sides of the valleys are formed 

 princij^ally by beds of the upper sandstone. 



On account of the folding of the series the beds are several times 

 repeated along a line normal to the general orientation of the moun- 

 tain range, which is north-south. These folds may be easily recog- 

 nized by the conglomerate outcrops which on an east-west line are 

 exposed at various places dipping now toward the east and now 

 toward the west. Thus, for example, in the section mentioned between 

 Santa Isabel and Lencoes the dip of the conglomerate is always 

 toward the east, and it forms the entire eastern slope of the range, 

 but on passing over the crest of the ridge it reappears with a western 

 dip after an interval in which a great thickness of the beds of the 

 lower sandstone is exposed. 



After another break occupied by the beds of the upper sandstone 

 (the conglomerate having passed beneath it) the same rock appears 

 again in the vicinity of Palmares, when the diamond washings like- 

 wise reappear. 



Judging from information gathered from others, the same thing 

 happens with the ranges and washings of Chapada Velha, Santo 

 Ignacio, and others that form a chain of diamond-bearing ridges 

 extending to near the Rio Sao Francisco. 



If it is true that the conglomerate, or ancient gravel, is the great 

 repository of diamonds and carbonados in the Lavras region, it fol- 

 lows that the stock of these minerals still in existence must be 

 enormous. The points of easiest attack thus far worked are insignifi- 

 cant in comparison with the masses of materials containing the 

 precious stones still untouched. 



It is evident, however, that only a relatively small part of this 

 mass can be worked with profit by the processes now in use. It 

 remains to be ascertained whether modern technology, by using the 

 hj'draulic power so abundant and so favorably situated in the region, 

 affords a method of operation less expensive than the value of the 

 products. 



