Physics and Chemistry of Minerals

, Volume 29, Issue 10, pp 668–679

Characterization of beryl (aquamarine variety) from pegmatites of Minas Gerais, Brazil

Authors

  • R. R. Viana
    • Departamento de Geologia, Universidade Federal de Ouro Preto, 35400 Ouro Preto, Brazil Tel.: +00-55-31-3559-1605
  • H. Jordt-Evangelista
    • Departamento de Geologia, Universidade Federal de Ouro Preto, 35400 Ouro Preto, Brazil Tel.: +00-55-31-3559-1605
  • G. Magela da Costa
    • Departamento de Quimica, Universidade Federalde Ouro Preto, 35400 Ouro Preto, Brazil E-mail: magela@iceb.ufop.br
  • W. B. Stern
    • Mineralogisch-Petrographisches Institut, University of Basel, Basel, Switzerland
ORIGINAL PAPER

DOI: 10.1007/s00269-002-0278-y

Cite this article as:
Viana, R., Jordt-Evangelista, H., da Costa, G. et al. Phys Chem Min (2002) 29: 668. doi:10.1007/s00269-002-0278-y

Abstract

Eight samples of the beryl variety aquamarine were selected from four pegmatites in the Governador Valadares and Araçuaí regions in northeastern Minas Gerais State, Brazil. These samples were fully characterized by chemical analysis, infrared and UV-visible spectroscopy, thermal analyses, and high-temperature X-ray diffraction (from room temperature up to 800 °C). Several physical and chemical properties of beryl were found to depend on the amount of water and ions residing in the structural channels. The thermal expansion coefficients from room temperature to about 800 °C are temperature-independent, with αa ≅ −3.2 × 10−6 ° C−1 and αc ≅ −8.7 × 10−6 ° C−1. The contraction of both a and c unit-cell parameters with increasing temperature and the shift of the infrared band centered at about 1200 cm−1 were tentatively ascribed to interactions between channel water and the silicate rings.The color of beryl seems to be dictated by the relative proportions of Fe3+ in the octahedralsites and of fe2+ in the channels. Thus, deep-blue samples have little Fe3+, whereas greener samples have more Fe3+ or less channel Fe2+.

Keywords BerylChannel constituentsThermal expansion

Copyright information

© Springer-Verlag Berlin Heidelberg 2002