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Formula: K3Al5(PO3OH)6(PO4)2.12H2O
Hydrated acid phosphate
Specific gravity: 2.26
Hardness: 1 to 2
Streak: White
Colour: Yellowish white
Environments
Localities
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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