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Formula: Na2Fe3+(SO4)2(OH).H2O
Hydrated sulphate containing hydroxyl
Crystal System: Orthorhombic
Specific gravity: 2.68 measured, 2.68 calculated
Hardness: 1½ to 2½
Streak: Pale yellow
Colour: Yellow, golden yellow, orange, pale brown
Solubility: Insoluble in cold water, decomposes in boiling water, soluble in acids (Dana)
Environments
Metasideronatrite is an uncommon alteration product of pyrite, typically
formed in arid climates but stably formed in sea-shore environments. Associated minerals include
sideronatrite, metavoltine,
ungemachite, ferrinatrite,
alunogen, natrojarosite,
pickeringite, sulphur,
tamarugite, aluminocopiapite,
metavoltine, mendozite,
kornelite and gypsum
(HOM). It reversibly rehydrates to sideronatrite depending on relative
humidity and exposure to sunlight
(Mindat).
Localities
At the type locality, Sierra Gorda, Antofagasta Province, Antofagasta, Chile, metasideronatrite occurs intimately
associated with metavoltine, and less commonly with
ferrinatrite, ungemachite,
alums and natrojarosite
(AM 23.733-734).
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