Mineralogy and technological characterization of two kaolin deposits from the Borborema Pegmatite Province, northeastern Brazil

Abstract

This research presents the mineralogical and chemical characterization and beneficiation study of two kaolin deposits from the Borborema Pegmatite Province, Brazil. Seven samples were collected and treated in two different beneficiation routes involving magnetic separation and chemical bleaching. The fractions obtained were studied by X-ray diffraction, X-ray fluorescence spectrometry, scanning electron microscopy, particle-size analyses, electron paramagnetic resonance and determination of optical properties. The samples are composed mainly of subhedral kaolinite in the form of booklets, as well as muscovite, quartz, microcline and illite impurities. The kaolinite structural formulae indicated significant replacement of Si4+ by Al3+ in tetrahedral sites and low replacement of Fe3+ by Al3+ in the octahedral sites. The first 30 min of chemical bleaching improved significantly the optical properties of kaolin, indicating that the process is more efficient than magnetic separation.

Mineralogy and chemistry of a new halloysite deposit from the Rio de Janeiro pegmatite province, south-eastern Brazil

“…In Brazil, the occurrence of halloysite appears to be restricted to the southeastern and southern regions of the country. In the north and northeast, no halloysite was detected in the kaolin sedimentary deposits of Capim River (Sousa et al, 2007) and Jari River (Montes et al, 2002) nor in the Borborema Pegmatite Province (Salgado- Campos et al, 2017Campos et al, , 2019. The occurrences of halloysite in Southern and Southeastern Brazil include those of the states of Minas Gerais , Espírito Santo (Wilson et al, 2006), São Paulo (Wilson et al, 1998), Paraná (Oliveira et al, 2007), Santa Catarina (Wilson et al, 1998), Rio Grande do Sul (Wilson et al, 2006) and Rio de Janeiro.…”

Mineralogical characterization of clay mineral assemblages from Rio de Janeiro pegmatites to identify kaolinite and/or halloysite deposits

“…Besides Brazil, kaolinitic kaolin deposits are found in the Hagendorf-Pleystein Pegmatite Province (Germany) [12] and the Spruce Pine deposit (USA) [13], while kaolinite and halloysite mixtures are found in the Bombowha deposit (Ethiopia) [14,15] and the Swat deposits (Pakistan) [16]. Brazil is the world's 7 th -leading kaolin producer, with 1.7 Mtpa [17], and its deposits are found mainly in the Capim River [18] and Jari River [19] sedimentary deposits in the North region, and in the primary deposits of the Borborema Pegmatite Province [20][21][22] and Oriental Pegmatite Province [23,24]. In the Brazilian Southeast and South regions, kaolin deposits from the Oriental Pegmatite Province are found in the State of Minas Gerais, primary deposits hosted in granites in São Paulo [25], primary deposits hosted in acid volcanic rocks in Paraná [26] and Santa Catarina [27], and primary deposits hosted in anorthosites in the Rio Grande do Sul [25].…”