The stability of onoratoite, Sb8O11Cl2, in the supergene environment

Adam J. Roper, Peter Leverett, Timothy D. Murphy, Peter A. Williams

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3 Citations (Scopus)


Synthesis and solubility studies of onoratoite have been undertaken to determine the role of this rare secondary phase in the immobilization of Sb and the conditions responsible for its formation in the supergene zone. Solubility studies were undertaken at 298.15 K. A value of ΔG θ f(Sb8O11Cl2, s, 298.15 K) =-2576 ±12 kJ mol-1 was derived. Calculations involving sénarmontite, Sb2O3, klebelsbergite, Sb4O4SO4(OH)2 and schafarzikite, FeSb2O4, show that onoratoite is a thermodynamically stable phase only at negligible activities of SO42-(aq) and low activities of Fe2+(aq), at low pH and very high activities of Cl-(aq). This explains why onoratoite is such a rare secondary phase and why it cannot exert any significant influence on the dispersion of Sb in the supergene environment.

Original languageEnglish
Pages (from-to)1671-1675
Number of pages5
JournalMineralogical Magazine
Issue number7
Publication statusPublished - Dec 2014
Externally publishedYes


  • onoratoite
  • antimony oxychloride
  • solubility
  • stability
  • chemical mineralogy
  • supergene zone


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