Formula:NaFe3+9+x(PO4)6(OH)11.3H2O (x ~ 0.33)
Hydrated phosphate containing hydroxyl
Specific gravity: 3.04 to 3.3
Colour: Greenish yellow, greenish white, yellow, light green
Kidwellite occurs in moderate abundance as a late-stage replacement of earlier phosphate minerals, such as
rockbridgeite and beraunite,
in novaculite deposits. Associated minerals include
chalcosiderite and goethite;
kidwellite is found rarely in phosphate-rich granite
or natrodufrénite may overgrow kidwellite in an epitaxial way,
(AM 64.242, Mindat, HOM).
At the type locality, Fodderstack Mountain, Norman, Montgomery county, Arkansas, USA, kidwellite is associated with rockbridgeite, dufrénite, eleonorite, beraunite and strengite in phosphate-bearing iron deposits (Mindat, Dana).
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