386 E. C. HARDER AND R. T. CHAMBERLIN 



Original or Bedded Ores 



Hard massive ore 



Soft powdery ore 



Larhinated or thin-bedded ore 

 Concentration Ores 



Canga 



Stream sand and gravel ores 



Rubble ore 



Enriched itabirite 



Leached carbonate 



Of these the bedded ores, especially the hard massive ores, are 

 by far the most important. Of the concentration ores the canga is 

 the principal type. 



Bedded ores. — Bedded iron ores are found in many places in 

 central Minas Geraes, but the most important deposits occur in the 

 region surrounding the headwaters of Rio Piracicaba, Rio Carmo, 

 Rio das Velhas, Rio Santo Antonio, and Rio Paraopeba, together 

 with their various branches and tributaries. This is the region in 

 which the Itabira iron formation has survived the extensive denuda- 

 tion which has swept away the post-Archean formations from 

 much of eastern Brazil, and where it still remains as a thick forma- 

 tion over considerable areas. The ore bodies occur at various points 

 along the belts of iron formation already described, both in the Ita- 

 bira iron formation proper, and in the iron-formation lenses in the 

 Piracicaba schist. They are not irregularly scattered throughout 

 the iron-formation areas, but are rather grouped in certain portions 

 with barren areas between. Thus groups of iron-ore deposits occur 

 north of Ouro Pre to on the east slope of the Serra do Carafa;"" on 

 the Rio Piracicaba west and northwest of the town of Villa Rio 

 Piracicaba; on the prominent peaks at Itabira de Matto Dentro; 

 along the ridge running from Sahara northeastward to Caethe and 

 southwestward beyond Bello Horizonte; at various points in the 

 area west of Itabira do Campo, and in the region west of Burnier 

 and north of Gongonhas do Campo. Smaller, less important 

 groups occur elsewhere in the district. 



The bedded ores occur as beds or lenses in the iron formation. 

 Some are thin and continuous for long distances, while others are 



' See map on p. 347, Part I of this article. 



