• journal_title：Clays and Clay Minerals
• Contributor：Simone Patrícia Aranha da Paz ; Rômulo Simões Angélica ; Roberto de Freitas Neves
• Publisher：Clay Minerals Society
• Date：2012-
• Format：text/html
• Language：en
• Identifier：10.1346/CCMN.2012.0600304
• journal_abbrev：Clays and Clay Minerals
• issn：0009-8604
• volume：60
• issue：3
• firstpage：265
• section：Articles

Bentonite deposits are rare in Brazil and most of their production comes from a single region. A new bentonite occurrence, the Formosa bentonite from northern Brazil, is described here. The occurrence is associated with altered Mesozoic volcanic rocks of the Parnaíba Sedimentary Basin, one of the largest continental flood basalt (CFB) provinces on Earth. The purpose of the present study was to evaluate the physical and chemical properties of a new smectite-bearing deposit in Brazil. Analysis has shown that the major mineral present in the Formosa bentonite is a dioctahedral smectite along with minor amounts of hematite, K-feldspar, and kaolinite. Quartz is absent. A Li⁺-saturation test (Hofmann-Klemen treatment) revealed a montmorillonite smectite; large interlayer-Mg²⁺ contents revealed by N₂ adsorption/desorption and cation exchange capacity results suggested a Mg-bentonite. This characterization helped to explore the structure-functionality (reactivity) relationship and to develop index tests for industrial applications and the research of new materials.

Use of this material as a desiccant-grade bentonite is envisaged (desiccant-grade bentonites contain Mg²⁺ and/or Ca²⁺ as the dominant exchangeable cations), or it could be activated with Na⁺ for use in many industrial applications (e.g. as a drilling fluid or for pelletizing iron ore). The large areal occurrence of the flood basalts suggests the possibility of very large deposits of these bentonites, a promising new exploration target for this class of industrial minerals in northern Brazil.