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Formula: Mn2+Fe3+2(PO4)2(OH)2.8H2O
Hydrated phosphate containing hydroxyl, paramorph of
pseudolaueite,
manganese-bearing mineral
Crystal System: Triclinic
Specific gravity: 2.94 measured, 2.48 calculated
Hardness: 3
Streak: White
Colour: Yellow to brownish yellow
Environments:
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,
hureaulite, strunzite,
laueite, pseudolaueite,
eosphorite, rockbridgeite,
strengite, diadochite,
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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