DIAMOND AND CARBONADO WASHINGS IN BRAZIL. 221 



occurrence of the diamond. The region is moderately hilly, with 

 an elevation of a little more than a hnndred meters, while the 

 highest serras to be seen on the horizon have no apparent relation 

 with the occurrence of diamonds in Rio Salobro. The entire region 

 is covered by a thick soil that supjjorts heavy forests, which conceal 

 the rocks and render geologic observations difficult. 



On the banks and at the falls of Eio Pardo, hardly 6 kilometers 

 from the Salobro washings, it was ascertained that the underlying 

 rocks of the region consist of a series of beds of sandstone and 

 argillaceous shales, with a heav}' bed of conglomerate made up of 

 rolled blocks of different kinds of granitic and gneissic rocks. This 

 series appears to have a thickness of several hundred meters and 

 has a strong eastward dip. 



In the beds of Rio Salobro and of its small tributaries this con- 

 glomerate is exposed at several places, and the washings thus far 

 opened are all in the immediate vicinity of its outcrops. In order 

 to verify the hjq^othesis of the conglomerate origin of the diamonds, 

 Mr. Pedro Benazet kindly had washed separately about 1^ cubic 

 meters of decomposed conglomerate, selected by the writer for the 

 purpose. The result was a diamond w^eighing 3 grains. It thus 

 seems to be beyond doubt that here in the littoral zone, as well as at 

 Lavras, the diamond is directly associated with the conglomerate, 

 which thus furnishes for j^rospecting a valuable guide, easily found 

 and recognized. 



It is evident that a formation as thick as that exposed on the 

 rivers Pardo and Salobro nuist have a wide distribution in this zone, 

 and there is a strong probability that at many, if not at all, points 

 where it crops out, it contains diamonds as it does on the Salobro. 

 Furthermore, this last district still affords a very large field for 

 mining operations. 



