The stability of onoratoite, Sb8O11Cl2, in the supergene environment. (December 2014)

• Record Type: Journal Article
• Authors: Roper, Adam J.; Leverett, Peter; Murphy, Timothy D.; Williams, Peter A.
• Is Part Of: Mineralogical magazine. Volume 78:Number 7(2014)
• Page Start: 1671
• Page End: 1675
• Publication Date: 2014-12
• Subjects: onoratoite, -- antimony oxychloride, -- solubility, -- stability, -- chemical mineralogy, -- supergene zone; Mineralogy -- Periodicals; Mineralogy -- Great Britain -- Periodicals; 549.05
• DOI: 10.1180/minmag.2014.078.7.10
• Languages: English
• ISSNs: 0026-461X

Abstract

Abstract: 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 ΔGf θ (Sb8 O11 Cl2, s, 298.15 K) = –2576 ±12 kJ mol –1 was derived. Calculations involving sénarmontite, Sb2 O3, klebelsbergite, Sb4 O4 SO4 (OH)2 and schafarzikite, FeSb2 O4, show that onoratoite is a thermodynamically stable phase only at negligible activities of SO4 2– (aq) and low activities of Fe 2+ (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.