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



The gold disseminated through the iron formation and resulting 

 canga formed the basis for most of the gold-mining operations in the 

 early years. A considerable proportion of the iron formation being 

 soft, it was washed almost as easily as stream gravels and, therefore, 

 was attractive to the early miners. 



Gold occurs as the native element disseminated in the Itabira 

 iron formation, as well as in the iron-formation lenses of the Piraci- 

 caba schist. It may be found in hard, or soft ore, or in itabirite, 

 but generally it occurs in the soft schistose phase of the iron forma- 

 tion known as " jacutinga " (see p. 389) ^ Most of the old workings 

 are in soft itabirite, or in soft, powdery ore, doubtless because of 

 the facility of operating in these formations. The gold is very un- 

 equally disseminated within the iron-formation belts, there being 

 large areas of iron formation in which little or no gold occurs, and 

 other places where it is found gathered in rich pockets. There is no 

 regularity in the distribution of the gold-bearing portions of the iron 

 formation and no apparent physical condition, unless it be differ- 

 ence in porosity, which would cause the localization in the places 

 where it occurs. Because of the irregularity of distribution and the 

 disseminated nature of the gold, this type of deposits has never 

 formed the basis of large individual operations. The deposits 

 were worked during the time of slavery because of the cheap- 

 ness of labor, but when slavery was abolished the workings were 

 abandoned. 



The gold occurring in the iron formation is of varying coarseness, 

 from fine dust, hardly visible to the naked eye, to fragments several 

 centimeters in length. Even large masses are reported to have 

 been found. The larger pieces have a porous, spongy texture and 

 contain intermixed particles of iron oxide and quartz. The par- 

 ticles of gold are generally elongated or platy in form, owing to 

 deposition along the lamination planes of the iron formation. 



Most of the gold occurring in the iron formation is very pure and 

 contains but very little alloyed silver or other metals. Locally, 

 however, there are occurrences of what is known as ouro hranco 

 (white gold), which consists of an alloy of gold and palladium. 



^ E. Hussak, "O Palladio e a Platina no Brazil," Annaes da Escola de Minas de 

 Ouro Preto, N. 8 (1906), p. 96, tr. by Miguel A. R. Lisboa, and Manoel A. R. Lisboa. 



