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Formula: K3Al5(PO3OH)6(PO4)2.12H2O
Hydrated acid phosphate
Crystal System: Trigonal
Specific gravity: 2.26 measured, 2.295 calculated
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, 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 Cioclovina cave, Boșorod, Hunedoara County, Romania,
hydroxylapatite is the earliest formed of the phosphate phases. Other
associated minerals in the fossil guano deposit include
taranakite,
monetite, crandallite,
tinsleyite,
leucophosphite, variscite,
francoanellite, gypsum,
bassanite, calcite,
vaterite, aragonite,
hematite, goethite,
birnessite, romanèchite,
todorokite and kaolinite
(CM 46.431-445).
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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