Hydrated phosphate containing hydroxyl, manganese mineral
Specific gravity: 2.94
Colour: Yellow to brownish yellow
Stewartite occurs in granitic pegmatites. It is a rare, low temperature, oxidation product
formed where triphylite has suffered retrograde alkali-leaching, oxidation and hydration. It
is associated with lithiophilite, triphylite,
phosphosiderite and iron-manganese oxides
(AM 59.1272-1276, HOM).
At the type Locality, the Stewart Mine, Tourmaline Queen Mountain, Pala Mining District, San Diego county, California, USA, stewartite occurs in a pegmatite associated with phosphosiderite, lithiophilite, jahnsite-(MnMnMn) and hureaulite (Mindat, Dana).
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