O. A. Derby — Occurrence of the Diamond in Brazil. :C> 



-strike and the same easterly dip, the unconformability of strat- 

 ification is not verv apparent and the close lithological resem- 

 blance of the two rocks throws one off his guard in regard 

 to it. Having recognized the unconformability of these beds 

 on the western slope of the range where in places the dip is in 

 opposite directions, I took pains to look for it elsewhere and 

 found many evidences of it on the eastern side as well. 



The junction of the two quartzites is in many places specially 

 interesting. The schistose beds of the lower quartzite enter 

 tooth-like into the mass of the upper, and the two former are 

 v homogeneous rock in which only the closest scru- 

 tiny can detect the line of junction, indicated by a few scattered 

 pebbles or a very slight difference in the intimate structure of 

 the beds. Away from the line of junction this discrimination 

 of the two series is more difficult and, if no pebbles can be 

 found in the rock, is often impossible, so close is the resem- 

 blance between the finer portions of the upper quartzite, and 

 the lower to which I would to restrict the name of itacolumite.* 



The relations of series c and d have not been clearly worked 

 out as the two have not been seen in contact, and it is possible 

 that they should be united. The differences in the lithological 

 - of the rock ami in their distribution is, however, 

 against this view. The limestone of series d is the only rock 

 of the region that has afforded fossils. At Bom Jesus da 

 Lapa. on the Sao Francisco, some distance to the northward I 

 found specimens of the corals Faun-ite* ..no ('/,</ f, /,_=>,• which indi- 

 catr Silurian or Devonian age. Liais reported fossil cirrip-'ds 

 of the genus f'vUinpes in the same limestone at Lapa do Urubu 

 on the Rio das Velhas, but at this locality I only found plates 

 of white calcite which might <>• rni.-faki i for fossils. The fos- 

 sil oyster of the same author from the sandstone of the Abacte* 

 'series ■■) appears to be based on structure lines in the rock. I 

 failed to find any evidence in support of his view of the Secon- 

 dary age of these rocks, and on the contrary have direct evidence 



These preliminaries are necessary for a correct appreciation 

 of the phenomena presented in the \. mis • asl igs which will 

 now be described. The miners established a distinction, which 

 it is convenient to retain, between river washings (servicos do 

 -io) and prairie washings (servicos do campo). Of the former the 

 most famous are in the bed of the Jequetinhonha where I had 

 an opportunity of examining three, the only ones that have 

 born worked of late years. 



These mines are situated to the eastward and southeastward 



