Metavivianite

minerals

kryzhanovskite

triphylite

vivianite

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.
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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