Abstract
One of the most important problems facing the gold industry is that the placer and free milling gold ores are almost terminating. Hence, the use of refractory ores has been increased during the recent years. In general, gold refractory ores occurs in various types of deposits associated with a range of minerals. Among the refractory ores, the sulfide type is the most common. The methodology employed in the mining process depends on the mode of occurrence of the ore and on the particle size, shape and degree of purity of the auriferous species. We have undertaken a mineralogical investigation of a representative sample of a complex gold mining ore collected in the municipality of Princesa Isabel, Paraiba, Brazil, using X-ray fluorescence spectrometry, X-ray diffractometry, infrared spectroscopy, inductively coupled plasma-atomic emission spectrometry and the Fire Assay. The results showed that the arsenic content of the ore was closely related to the gold content, and that the occurrence of “invisible gold” was associated primarily with pyrite and secondarily with arsenopyrite. The sulfur content of the ore was directly related to its refractoriness. It is concluded that gold mineralization in the study area is mainly of the gold-quartz-sulfide veins (lode gold), while the gold found in the mini-fractures of the deposits is probably associated with the hydrothermal processes that occurred in the region.
Highlights
Gold is primarily a metal of wealth and commerce, it is has a wide range of industrial applications in, for example, electronics, biomedicine and space engineering
The specific technologies employed in the mining process depend on the type of gangue associated with the metal and on the particle size, shape and degree of purity of the auriferous species
While the state of Paraíba is not noted for gold production, the Cachoeira de Minas region located in the municipality of Princesa Isabelre presents a significant resource of the precious metal
Summary
Gold is primarily a metal of wealth and commerce, it is has a wide range of industrial applications in, for example, electronics, biomedicine and space engineering. Auriferous ores generally contain very low concentrations of the precious metal (1 to 20 ppm), the mining of gold requires complex processes involving sampling, analysis and selective extraction [1]. While the state of Paraíba is not noted for gold production, the Cachoeira de Minas region located in the municipality of Princesa Isabelre presents a significant resource of the precious metal. This area is rich in quartz, limonite, goethite, pyrite, chalcopyrite, galena, sphalerite, covellite, cerussite and arsenopyrite. Previous chemical analyses have shown that the amount gold available in auriferous ores shows a wide variation with values ranging from traces up to 34 g/ton [3]
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