Kidwellite

minerals

rockbridgeite

dufrenite

beraunite

Formula:NaFe3+9+x(PO4)6(OH)11.3H2O (x ~ 0.33)
Hydrated phosphate containing hydroxyl
Specific gravity: 3.04 to 3.3
Hardness: 3
Streak: Yellow
Colour: Greenish yellow, greenish white, yellow, light green
Environments

Pegmatites
Hydrothermal environments

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 rockbridgeite, dufrénite, beraunite, strengite, chalcosiderite and goethite; kidwellite is found rarely in phosphate-rich granite pegmatites. Dufrénite or natrodufrénite may overgrow kidwellite in an epitaxial way, and vice-versa (AM 64.242, Mindat, HOM).

Localities

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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