Physics and Chemistry of Minerals

, Volume 40, Issue 4, pp 331–340

A comparative study of the thermal behaviour of length-fast chalcedony, length-slow chalcedony (quartzine) and moganite

  • Patrick Schmidt
  • Aneta Slodczyk
  • Vanessa Léa
  • Anne Davidson
  • Simon Puaud
  • Philippe Sciau
Original Paper

DOI: 10.1007/s00269-013-0574-8

Cite this article as:
Schmidt, P., Slodczyk, A., Léa, V. et al. Phys Chem Minerals (2013) 40: 331. doi:10.1007/s00269-013-0574-8

Abstract

The thermal behaviour of silica rocks upon heat treatment is dependent on the constituent minerals and petrographic texture types. These constituents can be shown to be mainly quartz in the form of two types of chalcedony (Length-fast (LF) chalcedony and Length-slow (LS) chalcedony, the latter also being termed quartzine) and moganite. Even though the thermal behaviour of LF-chalcedony is well understood, major uncertainties persist concerning the high-temperature behaviour of LS-chalcedony and moganite. We present here a comparative study of these three constituents of common silica rocks. Our results show that the chemical reaction is the same in all three, Si–OH + HO–Si → Si–O–Si + H2O, but that the reaction kinetics and activation temperatures are very different. LS-chalcedony begins to react from 200 °C upwards, that is at temperatures 50 °C below the ones observed in LF-chalcedony, and shows the fastest reaction kinetics of this ‘water’ loss. Chemically bound water (SiOH) in moganite is more stable at high temperatures and no specific activation temperature is necessary for triggering the temperature-induced ‘water’ loss. Moganite is also found to act as a stabilizer in silica rocks preventing them from temperature-induced fracturing. These findings have implications for the study of potential heat treatment temperatures of silica rocks (in industry and heritage studies), but they also shed light on the different structures of SiO2 minerals and the role of OH impurities therein.

Keywords

Silica rocks Moganite Chalcedony Quartzine Silanole (SiOH) Heat treatment 

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Patrick Schmidt
    • 1
  • Aneta Slodczyk
    • 2
  • Vanessa Léa
    • 3
  • Anne Davidson
    • 4
  • Simon Puaud
    • 5
  • Philippe Sciau
    • 6
  1. 1.Muséum national d’histoire naturelle, Dept. de Préhistoire UMR 7194Centre de spectroscopie infrarougeParis Cedex 05France
  2. 2.Laboratoire de dynamique, interactions et réactivité (LADIR), UMR 7075, CNRSUniversité Pierre et Marie Curie (UPMC)-Paris 6Paris Cedex 05France
  3. 3.TRACES, UMR 5608, Université Toulouse II le MirailToulouse CEDEX 9France
  4. 4.Laboratoire de Réactivité de Surface (LRS), UMR 7197, CNRSUniversité Pierre et Marie Curie (UPMC)-Paris 6Ivry sur SeineFrance
  5. 5.Muséum national d’histoire naturelle, Dpt. de Préhistoire UMR 7194 CNRSParisFrance
  6. 6.CEMES, CNRS UPR 8011, Université de ToulouseToulouseFrance