Specimen data for Cacoxenite

Tom Mortimer catalog number: u1023

Identification method: EDS analysis, two analyses shown. Both of these analyses are from the specimen area shown in the NH display specimen photo. Note the substantial variation in the aluminum content.

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Notes: Cacoxenite, Fe³⁺₂₄Al[(OH)₁₂|O₆|(PO₄)₁₇] · 17H₂O, and beraunite, Fe³⁺₅[(OH)₅|(PO₄)₄] · 4H₂O, have very similar chemistry. Aluminum is listed in the cacoxenite formula and per mindat, it is an "essential element." Some specimens in the author's collection of cacoxenite-like "brown fur" on rockbridgeite, were thought to be cocoxenite, however, EDS analysis of these specimens lack any aluminum response. These may be beraunite (normally greenish when fresh) that has oxidized to a tan-brown color. Cacoxenite from world-wide localities is generally yellow.