Jump to ContentJump to Main Navigation
Show Summary Details
More options …

American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian


IMPACT FACTOR 2018: 2.631

CiteScore 2018: 2.55

SCImago Journal Rank (SJR) 2018: 1.355
Source Normalized Impact per Paper (SNIP) 2018: 1.103

Online
ISSN
1945-3027
See all formats and pricing
More options …
Volume 88, Issue 10

Issues

Thermochemistry of guest-free melanophlogite

Alexandra Navrotsky
  • Corresponding author
  • Thermochemistry Facility and NEAT ORU, University of California at Davis, Davis California 95616, U.S.A.
  • Email
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Hongwu Xu
  • Thermochemistry Facility and NEAT ORU, University of California at Davis, Davis California 95616, U.S.A.
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Eric C. Moloy
  • Thermochemistry Facility and NEAT ORU, University of California at Davis, Davis California 95616, U.S.A.
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Mark D. Welch
  • Division of Mineral Sciences and Systematics, Department of Mineralogy, The Natural History Museum, London SW7 5BD, U.K.
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
Published Online: 2015-03-31 | DOI: https://doi.org/10.2138/am-2003-1026

Abstract

Melanophlogite is a naturally occurring clathrasil possessing a framework of linked silicate tetrahedra surrounding small, isolated cages, which can host small molecules. The energetics of a guest-free natural sample was determined by oxide-melt solution calorimetry. Melanophlogite is energetically metastable with respect to α-quartz by 9.5 ± 0.5 kJ/mol, a value similar to that for amorphous silica and for synthetic small-pore zeolitic silicas (Petrovic et al. 1993, Piccione et al. 2001). Thus, its occurrence in nature, for example in environments where it can occlude volcanic gases, is reasonable on energetic grounds.

Molecular modeling of the internal pore volume of melanophlogite confirms that this enthalpy follows the trend previously established for a variety of silica zeolites, which defines an internal surface energy of 0.093 ± 0.010 J/m2, similar to that of the external surface energy of amorphous silica. Thus melanophlogite, despite its unique topology and isolated cages, behaves energetically as predicted from the enthalpies of more-open zeolitic frameworks.

About the article

Received: 2003-06-09

Accepted: 2003-06-27

Published Online: 2015-03-31

Published in Print: 2003-10-01


Citation Information: American Mineralogist, Volume 88, Issue 10, Pages 1612–1614, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am-2003-1026.

Export Citation

© 2015 by Walter de Gruyter Berlin/Boston.

Comments (0)

Please log in or register to comment.
Log in