Ni-phyllosilicates (garnierites) from the Falcondo Ni-laterite deposit (Dominican Republic): Mineralogy, nanotextures, and formation mechanisms by HRTEM and AEM

Cristina Villanova-De-Benavent, Fernando Nieto, Cecilia Viti, Joaquín A. Proenza, Salvador Galí, Josep Roqué-Rosell

Research output: Contribution to journalArticle

Abstract

Ni-bearing magnesium phyllosilicates (garnierites) are significant Ni ores in Ni-laterites worldwide. The present paper reports a detailed TEM investigation of garnierites from the Falcondo Ni-laterite deposit (Dominican Republic). Different types of garnierites have been recognized, usually consisting of mixtures between serpentine and talc-like phases that display a wide range of textures at the nano-meter scale. In particular, chrysotile tubes, polygonal serpentine, and lizardite lamellae are intergrown with less crystalline, talc-like lamellae. Samples consisting uniquely of talc-like and of sepiolitefalcondoite were also observed, occurring as distinctive thin lamellae and long ribbon-shaped fibers, respectively. HRTEM imaging indicates that serpentine is replaced by the talc-like phase, whereas TEM-AEM data show preferential concentration of Ni in the talc-like phase. We suggest, therefore, that the crystallization of Ni-bearing phyllosilicates is associated with an increase in the silica activity of the system, promoting the replacement of the Ni-poor serpentine by the Ni-enriched talc-like phase. These results have interesting implications in material science, as garnierites are natural analogs of Ni-bearing phyllosilicate-supported synthetic catalysts. Finally, SAED and HRTEM suggest that the Ni-bearing talc-like phase corresponds to a variety of talc with extra water, showing larger d001 than talc (i.e., 9.2-9.7 Å), described as "kerolite"-"pimelite" in clay mineral literature.

Original languageEnglish
Pages (from-to)1460-1473
Number of pages14
JournalAmerican Mineralogist
Volume101
Issue number6
DOIs
Publication statusPublished - 1 Jun 2016

Keywords

  • "kerolite"-"pimelite"
  • chrysotile
  • garnierites
  • HRTEM
  • lizardite
  • Ni-laterites
  • polygonal serpentine
  • sepiolite-falcondoite

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