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Formula: Fe2+Fe3+2(PO4)2(OH)2.6H2O
Hydrated normal phosphate, paramorph of
ferrostrunzite. The prefix "meta"
indicates that the mineral is a dehydration product of vivianite.
Crystal System: Triclinic
Specific gravity: 2.69 calculated
Hardness: 1½ to 2
Streak: Blue or greenish blue
Colour: Dark blue to blue-black; Dark green to green-black
Environments
Pegmatites
Sedimentary environments
Metavivianite is a secondary mineral typically formed from
oxidising vivianite. It occurs in complex
granite pegmatites, in bogs and soils (HOM), in phosphate veins
in ironstone and in phosphatic sedimentary units (Mindat).
Common associates include anapaite and
siderite
(Mindat).
Localities
At the Chickering Mine, Walpole, Cheshire county, New Hampshire, USA, metavivianite occurs as crystals in seams in
massive quartz that has thin layers of
vivianite. It has also been found as a scaly rind over a core of
vivianite in vugs of siderite,
along with minor quartz
(R&M 90-5.419).
At the type locality, the Big Chief Mine, Glendale, Keystone Mining District, Pennington county, South Dakota, USA,
metavivianite occurs as a late stage oxidation product of vivianite in a
granite pegmatite
(Mindat).
Crystals of primary triphylite
to 6 feet have been altered by late-stage pegmatitic solutions to form
secondary minerals, including
ludlamite, hureaulite,
beraunite, rockbridgeite,
laueite, heterosite,
purpurite, strunzite and
metavivianite. The metavivianite occurs on a specimen of massive
triphylite containing veinlets of
spessartine-rich garnet,
pyrrhotite, sphalerite and
quartz. The surface of the triphylite
is pitted with solution cavities to 1 mm. The metavivianite occurs in these cavities, intimately intergrown with
kryzhanovskite, which is the only mineral observed to be in an apparent
equilibrium with metavivianite, although hureaulite is present in some
other cavities
(AM 59.896-899).
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