Sideronatrite and Metasideronatrite Efflorescence Formed in a Coastal Sea-Spray Environment

L. A. J. Garvie
Department of Geology, Arizona State University, Tempe, AZ 85287-1404, USA

Abstract: Sideronatrite [Na2Fe(SO4)2(OH)·3H2O] occurs as yellow botryoidal encrustations on low cliffs of weathered pyrite-bearing mudstones at Barton-on-Sea, Hampshire, England. Extensive areas of the cliffs, up to ∼100 m2, are coated with sideronatrite and its low solubility in cold water secures its longevity. Dry samples of sideronatrite convert readily to metasideronatrite [Na2Fe(SO4)2(OH)·H2O], the reaction to sideronatrite being reversible. Sideronatrite, it is suggested, forms as a result of weathering of pyrite that is present in the argillaceous sediments and reaction with Na from the sea-salt spray.

Keywords: sideronatrite • metasideronatrite • pyrite • weathering • efflorescence

Mineralogical Magazine; October 1999 v. 63; no. 5; p. 757-759; DOI: 10.1180/002646199548763
© 1999, The Mineralogical Society
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