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

Cave deposits

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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