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Formula: Ca9Mg(PO3OH)(PO4)6
Anhydrous normal phosphate
Crystal System: Trigonal
Specific gravity: 3.12 measured, 3.102 calculated
Hardness: 5
Streak: White
Colour: Colourless, grey-white, light pink, light yellow; colourless in transmitted light
Solubility: Readily soluble in dilute acids
Environments
Pegmatites
Guano deposits
Meteorites
Whitlockite is an uncommon secondary mineral in complex zoned
granite pegmatites, in phosphate rock deposits, in caves where it is
formed from leached
guano, and in chondrite meteorites. In
pegmatites it is associated with
ludlamite, fairfieldite,
triphylite, siderite,
apatite and quartz. In caves and islands it is
associated with
hydroxylapatite. In meteorites
it is associated with
stanfieldite, farringtonite and
brianite
(HOM)
At the Los Monges Island in the Caribbean Sea (Venezuela dependency), whitlockite has been found in phosphate rock, forming soft, earthy
masses under a botryoidal crust of monetite. In two instances the whitlockite occurred
as pseudomorphs after brushite and
gypsum
(AM 28.215-232).
At the type locality, the Palermo Number 1 Mine, Groton, Grafton county, New Hampshire, USA, whitlockite was found as a late
hydrothermal mineral
in altered triphylite in a granite pegmatite,
associated with xanthoxenite, triphylite,
siderite, quartz,
ludlamite, fairfieldite,
brazilianite, amblygonite,
childrenite-eosphorite and
apatite (Mindat, AM 34.692-705, Dana). The sequence of formation was whitlockite and
quartz, then rhodochrosite then
apatite and lastly a zeolite
(AM 26.145-152).
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