Images
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).
Localities
At the Fonte da Cal Mine, Bendada Mines, Bendada, Sabugal, Guarda, Portugal, stewartite has been found with
laueite, strunzite,
hureaulite and
phosphosiderite
(Mindat photo).
Stewartite from the Fonte da Cal Mine -
Image
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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