158 SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



those of Serro do Frio or Diamantina, Rio Abaete, Bagagem, and Grao Mogol ; of these, 

 the first, that of Serro do Frio or Diamantina is the most important. 



A sketch-map, after De Bovet, of the district of Serro do Frio or Diamantina, is 

 given in Fig. 35. The area is roughly elliptical in outline, the longer axis, stretching from 

 Serro in the south to the Rio Caethe Mirim in the north, being about fifty miles in length ; 

 while the shorter axis, from the Rio Jequetinhonha in the east to a line drawn parallel to 

 the Rio das Velhas through the villages of Dattas and Parauna, is about twenty-five miles. 

 It is a wild mountain district traversed by the northern end of the Serra do Espinha^o ; 

 this mountain range runs parallel to the meridian, and forms the watershed separating the 

 Rio de Sao Francisco and its tributary the Rio das Velhas from the Rio Jequetinhonha and 

 the Rio Doce. The district forms, roughly speaking, a plateau, the rugged margins of which 

 are cut by deep, steep-sided valleys. The principal town, Tejuco, which since the discovery 

 of diamonds has been known as Diamantina, is situated at a height of 4000 feet above sea 

 level and in latitude 18° 10' S. and longitude 43° 30' W. of Greenwich ; the district of 

 which it is the capital is now usually known by the same name. 



The diamonds occur both on the plateau itself and in the valleys which cut into it ; 

 the richest and best known of these river valleys is that of the Rio Jequetinhonha, with its 

 two branches Jequetinhonha do Campo and Jequetinhonha do Matto (Rio das Pedras) rising 

 in the Serro do Itambe. The general direction of this river is south-west to north-east, its 

 mouth is in the Atlantic seaboard, near to Belmonte, the latitude of which is about 16° S., 

 and in the lower part of its course it is known as the Rio Belmonte. It yields diamonds 

 from its source down to Mendanha, the stones being found not only in the main river but 

 also in its tributaries. While the tributaries on the right bank, such for instance as the 

 Rio Capivary and Rio Manso, which do not rise on the plateau of Diamantina, are poor in 

 diamonds, the tributaries of the left bank which have their sources on this plateau are rich 

 in diamonds, the Ribeirao do Inferno, Rio Pinheiro, Rio Caethe Mirim, and to a less degree 

 the Rio Arassuahy, being worthy of special notice. Other important diamond-bearing 

 streams are a few small water-courses flowing westward from the plateau directly or indirectly 

 into the Rio das Velhas, a tributary of the Rio de Sao Francisco; of these may be 

 mentioned the Rio das Dattas, Rio do Ouro Fino, ]{io do Parauna with its tributary the 

 Ribeirao do Coxoeira, and especially the Rio Pardo Pequena, which has yielded a large 

 number of extremely beautiful stones, and is probably, after the Jequetinhonha, the most 

 important of all. 



Next in importance come the deposits of the Rio Jequetahy and the Seri-a de Cabrol to 

 the north-west of Diamantina ; these are separated from the deposits previously mentioned 

 by a zone from which diamonds are absent. With these deposits may be mentioned a 

 small working in the Jequetinhonha valley, about sixty miles below Diamantina. An 

 occurrence which is remarkable in being completely isolated from the other diamond-yielding 

 localities is that at Cocaes, where a few small diamonds have been found ; this is situated 

 considerably to the south of Diamantina, and only thirty miles north of Ouro Preto, the 

 capital of the State of Minas Geraes. 



Another locality which must be specially noticed is the basin of the Rio Doce, on the 

 east side of the Serra do Espinha^o. The river basin is separated from the rich diamond 

 district of the Rio Jequetinhonha by only a narrow mountain ridge, but in spite of this close 

 proximity, only an insignificant number of stones have been found here, the explanation of 

 which will be given later. 



To the west of the Diamantina district is the Eio Abaete, a tributary on the left 

 bank of the Rio de Sao Francisco ; this river is fed by the Rio Fulda and Rio Werra, and 



