Hydrated acid phosphate
Specific gravity: 2.26
Hardness: 1 to 2
Colour: Yellowish white
In unnamed caves at Paddy's River Cu mine, Cotter River, Australian Capital Territory, Australia, francoanellite occurs with alunite, aragonite, berlinite, apatite variety collophane, crandallite, gypsum, huntite, hydromagnesite, leucophosphite, nesquehonite, niter and nitrocalcite (HOM).
At the type locality, the Grotte di Castellana, Castellana Grotte, Metropolitan City of Bari, Apulia, Italy, francoanellite occurs as nodular aggregatesto 0.2 mm in diameter, or as very soft, earthy masses, at the contact of "terra rossa" with bat guano in the karst cave (AM 61.1054). It is an alteration product probably formed by reaction between bat guano and clay minerals, and associated with its hydrate taranakite (HOM).
At the Grotta della Rondinella, Polignano a Mare, Metropolitan City of Bari, Apulia, Italy, francoanellite is associated with taranakite, hydroxylapatite and brushite (HOM).
At the Farallon Islands, San Francisco county, California, USA, francoanellite occurs in soils developed on granite debris and bat guano mixtures, by reaction of phosphate-rich sea mist with clay minerals (HOM).
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